The Smooze was a gargantuan slime-monster and the secondary antagonist of My Little Pony: The Movie - which took place in Generation 1 canon, making it very different from the current series and more in line with what modern audiences associate Care Bears or other "kid-friendly" cartoons to be.
The Smooze was nevertheless a geniunely terrifying being, especially giving the setting it was in - with the ability to grow to gargantuan sizes it spread across all of Ponyland and buried anything (living or not) in its path, completely ruining the land and turning once paradise-like fields and castles into barren wastelands - it also threw chunks of itself around that when attached to living beings turned them "mean" and "grumpy" (which despite the childish language is actually a more dangerous threat than one might think as removing living creatures' ability to care about each other can lead to apathy and despair (also without the ability to care for other beings people often develop sociopathic tendencies) ).
The Smooze was semi-sentient, able to form hands and faces but only able to express rage and malice - with animalistic roars and grunts (as well as limited speech (see trivia) ) - the ponies were originally powerless to stop the beast after the witch Hydia released it, with even the Rainbow being ultimately overwhelmed by the Smooze's power.
Yet just as the Smooze seemed ready to devour the last bit of Ponyland not corrupted by its presence the Flutter Ponies arrived - using their magic they managed to cast the Smooze away and undo its evil before lifting the mass of slime into the air and dumping it back into the volcano it came from along with Hydia and her two daughters.
- The Smooze is often compared to a Shoggoth from Lovecraftian lore, though it is unlikely the creators intended it to be this (considering the age group the movie was for) it does share some striking similarities.
- The Smooze, despite being the secondary antagonist, is arguably one of the most powerful villains the Ponies ever faced and was able to overpower the same Rainbow that destroyed the previous antagonist, Tirek - however it was no match for the magic of the Flutter Ponies.
- The Smooze was seen to have limited intelligence beyond simple rage as it arrogantly states "you can't stop me!" and "don't even try!" during its introductory song (it is also shown as taking delight in terrorizing the animals of Ponyland).
- The Smooze is also compared many times to Hedorah.
- The Smooze is also the inspiration to Pokémon characters: Grimer and Muk. 
- The Smooze was revamped in My Little Pony: Friendship is Magic.
- It makes a cameo appearance in the Friendship is Magic comic Nightmare Knights #1, which also features an appearance by its G4 counterpart.