How can we make a pumpkin, jack-o-lantern, or other halloween spirit, ghoul, or skeleton?

Here's some diabolical TikZ code:

documentclass[tikz,border=0]{standalone}
usetikzlibrary{backgrounds}
begin{document}
tikz[background rectangle/.style={fill=black},show background rectangle]foreachc[count=i from0]in{red!10!black,red!15!black,red!20!black,red!25!black,red!30!black,red!35!black,red!40!black,red!45!black,red!50!black,red!55!black,red!60!black,red!65!black,red!75!black,red!75!black!75!orange,red!75!black!50!orange,red!75!black!25!orange,red!75!black!5!orange,orange,orange!75!yellow,orange!50!yellow,orange!25!yellow,yellow,yellow!75,yellow!50,white}clip[preaction={fill=c},xscale=1-i/100,yshift=(i>0)*1.5](-6,-7)(6,3)foreachx in{1,-1}{[xscale=x](0:1)to[bend right]++(315:2)to[bend right]++(60:4)to[bend right,looseness=0.5]cycle}[shift=(270:i/15),yscale=1-i/50](0:5)arc(360:330:5 and 3)foreachi in{330,300,270,240}{arc(i:i-10:5 and 3)--(i-15:5 and 5)--(i-20:5 and 3)arc(i-20:i-30:5 and 3)}arc(210:180:5 and 3)arc(180:195:5 and 6)foreachi in{195,225,255,285,315}{arc(i:i+10:5 and 6)--(i+15:5 and 4)--(i+20:5 and 6)arc(i+20:i+30:5 and 6)}arc(345:360:5 and 6)--cycle;
end{document}

And this may take until next Halloween to compile:

documentclass[tikz,border=0]{standalone}
usetikzlibrary{decorations,backgrounds}
tikzset{pics/flame/.style 2 args={code={
  fill [fill=#1, yscale=1-#2/4, xscale=1-#2/5, rotate=rand*5]
    (0:.5+rnd) coordinate (a) arc (360:180:1 and 1) 
    .. controls ++(90:rnd)            and ++(270:rnd) .. (90+rand*5:2+rnd*2)
    .. controls ++(270+rand*5:.5+rnd) and ++(90+rand*5:.5+rnd) .. (a) 
    pgfextra{pgfgetpathflamegloballetflame=flame};
  foreach l in {1,...,20}
    draw [draw=#1, line width=l/2, draw opacity=1/10] pgfextra{pgfsetpathflame};
}}}
pgfdeclaredecoration{flames}{burn}{
  state{burn}[width=pgfdecorationsegmentlength]{
     pic {flame={flame}{pgfdecorationsegmentamplitude}};
   }
}
colorlet{flame}{red}
begin{document}
foreach i in {1,...,5}{
begin{tikzpicture}[background rectangle/.style={fill=black}, show background rectangle, line join=round]
useasboundingbox (-20,-20) rectangle (20,20); 
foreach c [count=x from 0] in {red!50!black, red!75!black, orange, yellow}{
  colorlet{flame}{c}
  draw [decoration={flames, segment length=1.5cm-x*0.125cm, amplitude=x}, decorate] 
    circle [radius=15]
    (270:15) -- (54:15) -- (198:15) -- (342:15) -- (126:15) -- cycle;
}
end{tikzpicture}
}
end{document}

tikz?, pstricks? everyone knows the underworld used picture mode.

documentclass{article}
usepackage{color}
usepackage{pict2e}
pagecolor[RGB]{255,177,69}
begin{document}

begin{picture}(120,200)
thicklines
put(100,100){circle{150}}

put(70,130){line(1,-1){10}}
put(70,130){line(-1,-1){10}}
put(60,120){line(1,0){20}}

put(130,130){line(1,-1){10}}
put(130,130){line(-1,-1){10}}
put(120,120){line(1,0){20}}

put(100,90){line(1,-1){10}}
put(100,90){line(-1,-1){10}}
put(90,80){line(1,0){20}}

put(70,50){line(1,0){60}}
put(70,50){line(-2,1){5}}
put(130,50){line(2,1){5}}
end{picture}

end{document}

documentclass[tikz]{standalone}
usetikzlibrary{decorations.pathreplacing}
begin{document}
begin{tikzpicture}defonehalf{
fill(0.25,0) to [bend right] ++(180:1) to [bend right] ++(330:1.5) to[bend right, looseness=0.5] cycle;
draw [decoration={expanding waves,angle=4,segment length=0.5pt},decorate] (-1cm,0.7cm) to[out=0,in=140] (0.7cm,-0.2cm);
fill (1.05cm,-1.1cm) to[out=270,in=180] ++(2mm,-0.4cm) to[out=0,in=0,looseness=0.5] cycle;
fill[preaction={draw,decorate},decoration={ticks}] (-0.3,-1.5) to[out=-30,in=180] (1,-2) to[bend left] (1,-3) to[bend left] cycle;}
onehalfbegin{scope}[cm={-1,0,0,1,(2,0)}]onehalfend{scope}
end{tikzpicture}
end{document}

A truly demonic entity would manually write its own postscript code.

%!PS-Adobe-2.0 EPSF-2.0
%%Title: pumpkin.eps
%%BoundingBox: 0 0 200 200
/tri {newpath 0 0 moveto 10 0 lineto 0 20 lineto -10 0 lineto closepath fill} bind def
1.0 0.6 0.25 setrgbcolor
1 setlinewidth
100 100 100 0 360 arc gsave stroke grestore fill
0 0 0 setrgbcolor
100 90 60 190 350 arc stroke
100 100 translate tri
-50 40 translate tri
100 0 translate tri
showpage
%EOF

documentclass[tikz,border=10pt]{standalone}
usetikzlibrary{calc,backgrounds}
usepackage{hieroglf}
newcommand*{llygaddienyddiwr}{textpmhg{He}}
pgfdeclarelayer{foreground}
pgfsetlayers{background,main,foreground}
% adapted (simplified version) from tex/generic/pgf/frontendlayer/tikz/libraries/tikzlibrarybackgrounds.code.tex
makeatletter
tikzset{%
  on foreground layer/.style={%
                execute at begin scope={%
                  pgfonlayer{foreground}%
                  lettikz@options=pgfutil@empty%
                  tikzset{every on foreground layer/.try,#1}%
                  tikz@options%
                },
                execute at end scope={endpgfonlayer}
  },
}
makeatother
tikzset{%
  pics/yr Angau/.style n args={2}{
        code={
          path  (-#2/4,-.55*#2)
                |- (-.15*#2,-.15*#2) coordinate (angau7)
                [out=-20, in=110] to (-.025*#2,-.25*#2) coordinate (angau8)
                [out=85, in=-85] to (0,-.1*#2) coordinate (angau9)
                [out=135, in=-100] to (-.125*#2,-.015*#2) coordinate (angau3)
                -| (-#2/4,#2/2) -| (.375*#2,-.55*#2) -- cycle;
          path [line cap=round, line width=.025*#2]
                  (0,-.5125*#2) coordinate (angau5) -- ++(-#2/6,.95*#2) coordinate [pos=.875] (angau4) coordinate [pos=.95] (angau1);
          path [draw=#1, fill=#1, line width=.005*#2, line join=miter]% llafn
                (angau1) [out=30, in=150] to ($(angau5) + (.375*#2,#2)$) [out=-30, in=135] to ++(.125*#2,-.1*#2) [out=135, in=30] to (angau4);
                path [angau clogyn={#1}{#2}]% corff & pen
                (-.2*#2,-#2/2)
                  [out=85, in=-110] to (angau7)
                  [out=160, in=-45] to (-.2*#2,-.115*#2)
                  [out=135, in=-135] to (-.2*#2,.075*#2)
                  [out=45, in=-135] to (-.05*#2,.125*#2)
                  [out=80, in=-80] to (-.075*#2,.2*#2)
                  [out=100, in=-150] to (.025*#2,.35*#2) coordinate (pen angau)
                  [out=-35, in=80] to (.125*#2,.2*#2)
                  [out=-100, in=170] to (.15*#2,.1*#2)
                  [out=-10, in=120] to (.3*#2,-#2/2)
                  [out=170, in=-10] to cycle;
          path [angau inner={#1}{#2}]% gwyneb
                (.025*#2,.325*#2) coordinate (pen angau1)
                  [out=-40, in=60] to (.025*#2,.125*#2) coordinate (angau6)
                  [out=120, in=-145] to cycle;
          begin{scope}% carn (neu 'dwrn'?)
                clip  (-#2/4,-.55*#2)
                  |- (angau7)
                  [out=-20, in=110] to(angau8)
                  [out=85, in=-85] to (angau9)
                  [out=135, in=-100] to (angau3)
                  -| (-#2/4,#2/2) -| (.375*#2,-.55*#2) -- cycle;
                path [draw=#1, line cap=round, line width=.025*#2]
                  (angau5) -- (angau1);
          end{scope}
          path [angau outer={#2}{#1}]% llewysau (llinellau)
                (angau6)
                  [out=-100, in=85] to (.025*#2,-#2/2)
                (angau7)
                  [out=-20, in=110] to (angau8)
                  [out=85, in=-85] to (angau9)
                  [out=135, in=-100] to (angau3)
                (.15*#2,-.02*#2)
                  [out=-60, in=30] to (.125*#2,-.175*#2) coordinate (angau10)
                  [out=-10, in=135] to (.275*#2,-.475*#2) coordinate (angau2);
          path [angau inner={#1}{#2}]% llawes chwith
                (angau8) [out=85, in=-85] to (angau9) [out=-85, in=-85] to cycle;
          path [angau inner={#1}{#2}]% llawes dde
                (angau10) [out=-10, in=135] to (angau2) [out=135, in=-20] to ($(angau10) + (-.005*#2,-.015*#2)$) [out=160, in=170] to cycle;
        }
  },
  pics/dienyddiwr/.style n args={2}{
        code={
          begin{scope}[on foreground layer]% carn (neu 'dwrn'?)
                path (-#2/4,-.55*#2)
                  |- (-.15*#2,-.15*#2) coordinate (dienyddiwr7)
                  [out=-20, in=110] to (-.025*#2,-.25*#2) coordinate (dienyddiwr8)
                  [out=85, in=-85] to (0,-.1*#2) coordinate (dienyddiwr9)
                  [out=135, in=-100] to (-.125*#2,-.015*#2) coordinate (dienyddiwr3)
                  -| (-#2/4,#2/2) -| (.375*#2,-.55*#2) -- cycle;
                begin{scope}
                  clip  (-#2/4,-.55*#2)
                        |- (dienyddiwr7)
                        [out=-20, in=110] to (dienyddiwr8)
                        [out=-85, in=-85] to (dienyddiwr9)
                        [out=135, in=-100] to (-.125*#2,-.015*#2) coordinate (dienyddiwr3)
                        -| (-#2/4,#2/2) -| (.375*#2,-.55*#2) -- cycle;
                  path [draw=#1, line cap=round, line width=.025*#2]
                  (-.05*#2,-.25*#2) coordinate (dienyddiwr5) -- ++(#2/4,.45*#2) coordinate [pos=.875] (dienyddiwr4) coordinate [pos=.95] (dienyddiwr1);
                end{scope}
          end{scope}
          path [draw=#1, fill=#1, line width=.005*#2, line join=miter]% llafn
                (dienyddiwr1)
                  [out=-35, in=-115] to ++(.2*#2,-.025*#2)
                  [out=-90, in=35] to ($(dienyddiwr4) + (.125*#2,-.175*#2)$)
                  [out=65, in=-35] to (dienyddiwr4);
          path [angau clogyn={#1}{#2}]% corff & pen
          (-.2*#2,-#2/2)
                [out=85, in=-110] to (dienyddiwr7)
                [out=160, in=-45] to (-.2*#2,-.115*#2)
                [out=135, in=-135] to (-.2*#2,.075*#2)
                [out=45, in=-135] to (-.05*#2,.125*#2)
                [out=80, in=-80] to (-.075*#2,.2*#2)
                [out=100, in=-150] to (.025*#2,.35*#2) coordinate (pen dienyddiwr)
                [out=-35, in=80] to (.125*#2,.2*#2)
                [out=-100, in=170] to (.15*#2,.1*#2)
                [out=-10, in=120] to (.3*#2,-#2/2)
                [out=170, in=-10] to cycle;
          path [angau inner={#1}{#2}]% gwyneb
                (.025*#2,.325*#2) coordinate (pen dienyddiwr1)
                  [out=-40, in=60] to (.025*#2,.125*#2) coordinate (dienyddiwr6)
                  [out=120, in=-145] to cycle;
          begin{scope}[on foreground layer]
                path [angau outer={#2}{#1}]% llewysau (llinellau)
                  (dienyddiwr7)
                        [out=-20, in=110] to (dienyddiwr8)
                        [out=85, in=-85] to (dienyddiwr9)
                        [out=135, in=-100] to (dienyddiwr3)
                  (.15*#2,-.02*#2)
                        [out=-60, in=30] to (.125*#2,-.175*#2) coordinate (dienyddiwr10)
                        [out=-10, in=135] to (.275*#2,-.475*#2) coordinate (dienyddiwr2);
                path [angau inner={#1}{#2}]% llawes chwith
                  (dienyddiwr8) [out=85, in=-85] to (dienyddiwr9) [out=-85, in=-85] to cycle;
                path [angau inner={#1}{#2}]% llawes dde
                  (dienyddiwr10) [out=-10, in=135] to (dienyddiwr2) [out=135, in=-20] to ($(dienyddiwr10) + (-.005*#2,-.015*#2)$) [out=160, in=170] to cycle;
          end{scope}
          path [angau outer={#2}{#1}]% clogyn (llinell canolog)
                (dienyddiwr6)
                  [out=-100, in=85] to (.025*#2,-#2/2);
          begin{scope}% llygaid
                  clip (pen dienyddiwr1) [out=-40, in=60] to (dienyddiwr6) [out=120, in=-145] to cycle;
                  path [fill=#1!25!darkgray, draw=#1!25!darkgray, line width=.005*#2]
                        ($(dienyddiwr6)!2/3!(pen dienyddiwr1) - (.03*#2,0)$) coordinate (llygad dienyddiwr chwith) +(.005*#2,0) coordinate (llygad dienyddiwr chwith1) circle (.013*#2 and .003*#2)
                        ($(dienyddiwr6)!2/3!(pen dienyddiwr1) + (.03*#2,0)$) coordinate (llygad dienyddiwr de) +(-.006*#2,0) coordinate (llygad dienyddiwr de1) circle (.013*#2 and .003*#2);
                  path [fill=#1, draw=#1, line width=.005*#2]
                        (llygad dienyddiwr chwith1) +(.003*#2,0) circle (.003*#2)
                        (llygad dienyddiwr de1) +(-.003*#2,0) circle (.003*#2);
                  node [#1, font=tiny, xscale=-.0075*#2, yscale=.0075*#2, inner sep=0pt, outer sep=0pt, anchor=center] at (llygad dienyddiwr chwith) {llygaddienyddiwr};
                  node [#1, font=tiny, scale=.0075*#2, inner sep=0pt, outer sep=0pt, anchor=center] at (llygad dienyddiwr de) {llygaddienyddiwr};
          end{scope}
        }
  },
  angau outer/.style n args={2}{draw=#2, line join=miter, line width=.005*#1},
  angau clogyn/.style n args={2}{angau outer={#2}{#1}, inner color=#1, outer color=black},
  angau inner/.style n args={2}{angau clogyn={#1!25!black}{#2}},
}
begin{document}
begin{tikzpicture}[background rectangle/.style={top color=black!35!red, bottom color=black!85!red}, show background rectangle]
  pic {yr Angau={darkgray}{50pt}};
  pic at (1,0) {dienyddiwr={red}{50pt}};
end{tikzpicture}
end{document}

A complete Halloween scene, in one line.

documentclass[12pt]{article}
usepackage{halloweenmath}
usepackage{mathabx}
begin{document}
[
bigpumpkinbigskullmathwitchmathghostmathbatrip
]
end{document}

(I just discovered the awesome halloweenmath package, and must now find a way to use it in my work.)

documentclass{article}

usepackage{tikz}
usepackage{halloweenmath}
newtheorem{definition}{Definition}
newtheorem{theorem}{Theorem}
newtheorem{formula}{Formula}
setlength{voffset}{-0.5in}
setlength{topmargin}{-0.2in}
setlength{textheight}{240mm}
setlength{textwidth}{142mm}
setlength{evensidemargin}{0.3in}
setlength{oddsidemargin}{0.3in}
usepackage[english,italian]{babel}
usepackage[T1]{fontenc}
usepackage[utf8]{inputenc}
usepackage{times}
usepackage{graphicx}
usepackage{color}
usepackage{tikz}
usepackage{textcomp}
usepackage{amsmath}
usepackage{mathabx}
usepackage{wasysym}
usepackage{pifont}

begin{document}

begin{tikzpicture}
fill [black!80, rotate=05] (1,0) ellipse (0.25cm and 1.0cm);
fill [black!80, rotate=-05] (-1,0) ellipse (0.25cm and 1.0cm);
draw (-4,-6) .. controls (-3,1) and ( -1,3) .. (0,3)
          .. controls (1,3) and (3,1) .. (4,-6);
draw (-4,-6) .. controls (-4.5,-6.5) and (-2.5, -6) .. (0,-6);
draw (4,-6) .. controls (4.5,-6.5) and (2.5,-6) ..  (0,-6);
end{tikzpicture}

Large {We wish you HAPPY HALLOWEEN!}

end{document}