The Undertale Effect 

The Undertale Effect is a cycle that any form of entertainment media community can fall into.
Essentially, the community will COMPLETELY over rate the show/game/book/movie/etc., and defend it as if it is their life. The community will almost always turn the lovable, funny characters into cringe, and rapidly spread throughout the internet.
The strange thing is that the only outlets to suffer from The Undertale Effect are those from something that by itself is great. The show/video game/movie/etc. is usually great, and has many redeeming qualities but it is overshadowed by the atrocious and toxic fanbase.
Quite obviously, this is based off of the worst case of this ever happening yet - Undertale. I won't get into it now, but the smallest peek into the (dead now) community will tell you.
This has infamously happened to: Steven Universe, Five Nights at Freddy's, Minecraft, and unfortunately even Rick and Morty.

Right now, Rick and Morty has fallen into the Undertale Effect. Just look at Musical.ly, the fan art, the cancerous reddit copypasta, etc.

The Undertale Effect by That_One_Dodgy_boi October 22, 2017

The Undertale Effect 

A term used when a video game or television show becomes unbearable to play/watch because of its fanbase.

"It sucks how badly the Undertale Effect ruined Rick and Morty."

The Undertale Effect by PhantomBird529 September 17, 2017

The Undertale effect 

Once something popular releases, the community and any content made about it WILL degrade and become worse overtime.

"hey have you noticed the twitter community on welcome home keeps getting worse?"
"That, my good friend is the undertale effect happening in practice"

The Undertale effect by AmnesiaPen May 6, 2023

The Undertale Effect 

By listening to undertale ost's your vrt increases by 100% causing you to get good kovaak's scores. Often people confuse it with 𝓪𝓲𝓶𝓫𝓸𝓽*.

*𝓪𝓲𝓶𝓫𝓸𝓽- a bot that aims.

Me: oh you got a good score on arc dodge switch?
My friend: yeah i used the undertale effect.
Me: oh that makes sense now

The Undertale Effect by Saltcult February 9, 2021