It spits out some COWBOY PLAYMOBIL's figurines....

I feed the Mimic a Truck filled with leather blankets.

It eats the truck, which falls into its stomach. As the truck is digested, it makes annoying beeping noises. The truck dissolves, but the blankets have gained sentience and now have the same stats as a rug of smothering, except that their intelligence is 13. The rugs climb out of the mimic, which then proceeds to throw up. Meanwhile, the rugs attack a random orc, and all of them fall into the mimic’s mouth.

I feed the mimic a live mongoose.

As it eats the mongoose it shapes back into it’s Druid form and banishes you to the elemental plane of earth.

I feed the mimic my most valuable possession.

It refuses to eat a plastic toy compass from the dollar store, and spits in your face.

I feed the mimic Mordekainen.

The mimic turns into a mordakainen's magnificent mansion house mimic

I feed the mimic a bowl of lucky charms

The mimic becomes lucky.

I feed the mimic everthing.

The mimic wants MOOOOOOORRRRRRE

I feed the mimic a picture of Leonardo Dicaprio and Leonardo Da Vinci, hugging. 

The Mimic stares at the painting, as it has a strange odour of polluted air and reluctantly eats it

I feed it itself (not sure if it has been done before. Don't yell at me if it has)

It has already!!!! Just kidding... i dunno...

it becomes twice as big. LOGIC. 

I feed the mimic Jack, Jim ,and Jose. 

It starts getting weary and falls asleep then wakes up with a hangover. 

I feed it the forgotten Realms.

As it swallows the forgotten realms, a half digested orc holding the shredded remains of the previously mentioned sentient blankets climbs out. The orc begins attacking everything in sight when suddenly a platoon of half digested zombies also climbs out of the mimic. The orc yells in defiance and flings the blankets at the zombies. The zombies, being undead, don’t react at all. Instead, they kill the orc and throw it back into the mimic. The Mimic burps and then grows bigger. As it does so, it transforms itself into a 5' by 5' anvil and eats the zombie platoon that previously climbed out.

I feed the mimic a tuna salad and pickle sandwich.

The mimic vomits all over you.In the vomit you find a mirror.you look in the mirror and nothing happens.

I feed it an sword

It can now shoot swords out its mouth like a gun. a sword gun ruuuun! Run before you get shot with a swo-...

I feed the mimic everything from party city. 

The mimic gets a party hat of greed, giving him the following trait:

HUNGRY:The mimic is always hungry and never full.

the only way to get rid of this hat is a wish spell or by feeding it... An egg salad sandwich?

I feed it a 2-square ball

The mimic eats the paradoxical 2 square ball, spitting out a set of 4 squares.

I feed the mimic Nightmare King Grimm

The mimic grows a lot of tentacles. 

I feed the mimic 4-ply toilet paper...

The mimic poops out a porta-john

I feed the mimic all the flavors of mtn dew.

The mimic gets excited and hyper after drinking the mtn dew. It then spits out some gold coins in payment.

I feed the mimic The Radiance

The mimic becomes a gold chest with diamond and ornate designs. 

I feed the mimic a dictionary ,but every word in it is spelled wrong ,and has the wrong definition. 

The mimic gets -3 on intelligence checks

I feed it Microsoft Teams