Is there a term for when fiction refers to fiction

Allusion, may be the term you are looking for.

Allusion is a brief and indirect reference to a person, place, thing or idea of historical, cultural, literary or political significance. It does not describe in detail the person or thing to which it refers. It is just a passing comment and the writer expects the reader to possess enough knowledge to spot the allusion and grasp its importance in a text. https://literarydevices.net/allusion/

While it does include things other than fiction for possible references, it's still fairly specific. The example you provided falls well within this definition. Perhaps "literary allusion" would be more fitting.

I think Allusion is the best term for this scenario, but there can be other world-breaking type of scenarios. I adore MetaFiction, so the link to Intertextuality is a good starting place, and if you have time, yes, TV Tropes can show you a zillion parallels.

Some more things to explore:

• https://en.wikipedia.org/wiki/Meta
• https://en.wikipedia.org/wiki/Fourth_wall
• https://en.wikipedia.org/wiki/Meta-reference
• https://en.wikipedia.org/wiki/Hypostasis_(literature) (this was averted -- the characters in E.T. still believe they are "real" -- but if not, could they cross fictional paths and use a transporter?
• https://en.wikipedia.org/wiki/Experimental_literature

There is the general term self-reflexive, referring to when something refers to itself. (Now, if I can find a reference...) Ah, here we go -- Websters:

marked by or making reference to its own artificiality or contrivance. self-reflexive fiction

If you haven't found the term you are looking for yet, it is "meta." This term derives from "metafiction."

From MW.com

1 informal : showing or suggesting an explicit awareness of itself or oneself as a member of its category : cleverly self-referential

2 informal : concerning or providing information about members of its own category

Your example fits more into definition 2, while other meta examples are more self-aware and even "break the fourth wall" to comment on themselves.

Examples of the use of "meta":

Why Rick and Morty gets so meta

‘Scream’ Turns 20: 10 Reasons It’s Still a Meta-Horror Masterpiece

Rick and Morty's Latest Meta Episode 'Bashes' Its Own Narrative

What’s The Meta? How The Cabin in the Woods Subverted Horror

8 Unapologetically Meta SF/F Novels