What is the hidden achievement in Little Alchemy?

According to the wikia page, you get this achievement for crafting one of the nine hidden gems.

There are 9 hidden gems in Little Alchemy. Creating one will get you the achievement "Is This Just Fantasy?"

The gems you can craft to get this achievement are:

• Astronaut Ice Cream (astronaut + ice cream)
• The Doctor (tardis + doctor)
• Tardis (space + time)
• Doge (dog + computer)
• Keyboard Cat (cat + music)
• Ninja Turtle (ninja + turtle)
• The One Ring (ring + volcano)
• Yeti (mountain + story OR mountain range + story)
• Nessie (story + lake)

_{(Combinations gotten from the wikia in conjunction with this site, as the wikia did not have Nessie)}