The mimic spits out a virtually indestructible orb that produces the effect of an antimagic field centered on itself. 

I feed the mimic a full set of devastation orbs. 

The mimic gets a bad case of indigestion, and belches up a few chunks of devastation gravel, which isn't nearly as effective.

I feed the mimic my last bottle of crystal Pepsi.

The mimic suddenly and violently blasts pie filling from its mouth, along with a crab suspended in Vaseline

I feed the mimic some orangutan parm.

The mimic spits out a gorilla and a chimpanzee. 

I feed the mimic a Smilodon. 

The mimic spits out a smiling man named Don.

I feed the mimic a hill giant who enjoys dancing to opera music.

After a long wait, the hill giant successfully escapes the mimic, but the mimic pounces on it and re-consumes it.  It then spits out a fat lady with a spear and a horned helmet. 

I feed the mimic a gittern. 

The mimic spits out the gittern and the gnome bard who owned the gittern.  The gnome plays you a song in thanks

I feed the mimic 10 strong men.

The mimic spits out Synthil's characters. 

I feed the mimic a set of colored pencils. 

The mimic spits out a portrait of you.  It is very realistic.

I feed the mimic a wand of wonder.

The mimic does a wondrous magic act, dazzling all around.

I feed the mimic the undertale fan base.

The mimic spits out Gollum. 

I feed the mimic a light crossbow that functions as a circlet of blasting that uses the wielder's attack bonus with the crossbow. 

 It spits out a young, but experienced, Tefling Ranger raised by Goliaths.

I feed the Mimic the Vampire Count Strahd von Zarovich.

It spits out a complete set of jungle drums, a superintelligent ape, an elephant, a toucan, some vines, some monkeys, and a half-dozen very tall trees.  Then, it spits out a recording studio.  Then, it spits out Carol Burnett, who does her Tarzan yell, pulls a chair out of the mimic, and sits in it.  Then, the mimic spits out a movie-theater popcorn machine and an equal amount, by volume, of unpopped popcorn and seasonings.  Then, it finally gets around to spitting out George of the Jungle. 

I pop a batch of popcorn and feed it to the mimic. 

The mimic spits out a bunch of hard corn kernels at your feet.

I feel the mimic three Magic Stones.

The mimic spits out this link. 

I feed the mimic the hopes and dreams of the D&D Beyond community. 

The mimic coughs up a puff of dust, followed by a few moths.

I feed the mimic a snow-dusted stuffed tiger wearing a red scarf.

A roll of parchment slips through the opening of the mimic's lid, like a sheet of printer paper. Written on the parchment is the sentence, "Let's go exploring!"

I feed the mimic another mimic.

The mimic spits out two mimics, which promptly attack. 

I feed the mimic a set of iron bands of binding and a mage-smith named Billaro. 

The mimic spits out a magic sword with the consciousness of the poor departed Billaro. It also spits back back out the iron bands of binding which unfortunately ensnare you.

I feed the mimic Ned Flanders.

The mimic opens it's mouth, shooting forth unbearably bright light which sears the image of stupid sexy Flanders into your retina for all eternity. 

I feed the mimic a shotgun.