It spits out another mimic

I feed the mimic a Tarrasque 

The Tarrasque eats the 1st Mimic, but fails attempting to eat the 2nd......

I feed the Mimic with a Goulash filled with hot spicy peppers.........

The mimic catches fire

I feed the mimic the corpse of a king from a forgotten kingdom

It spits out the king who is alive now.

I feed the mimic this thread.

It spits out the same thread but with a roper being fed things instead.

I feed the mimic all the main Bbegs.

It vomit all of the bbegs due to the intense bad taste.

I separate the vomited corpses of those BBEGs , taking 3 of them to add a chili pepper, and reagrup the corpses in a pizza.

I ffed the Mimic with that ""PIZZA""

It spits out Beowulf

I feed it Grendel

After eating the Grendel it spits out Crispin Glover. 

I feed it Glover. That video game from the '99.

The mimic eats the glover and spits out a Tarrasque that destroys everything around it and wanders off.

I feed the Mimic a Mimic

It sadly eats the mimic, feeling sorry for eating it’s own kind. You get a sad face and a spot on the naughty list.

I feed the mimic the meaning of life

The mimic seems to dance wildly, and starts to grow two more eyes..........

I feed the Mimic an entire Encyclopedia about "Breast Cancer"............

It spits out Nancy Brinker, who founded the Susan G. Komen organazation and named it in honour of her sister who died of breast cancer in 1980.

I feed the mimic my sweaty headband from the last colour run I participated in.

It spits out a game of Hedbanz 

I feed the mimic itself

The mimic spits out a black hole

I feed give the mimic a bouquet of roses

you all died.

the mimic is now a black hole

The black hole spits out a mimic.

I feed it a comma (,) .

it devores the comma, and spits out the homebrew monster unknown (nightmare)

What do you feed it?

a boomer

It spits out a new baby, starting a new generation

i feed the mimic the answer to the question of life, the universe, and everything