The mimic breathes fire because of the spiciness of the dish. You are left in a pile of ashes. 

I feed the mimic the old batteries that I just used for my De-Cubeinator, which turned me back into me. 

The mimic starts acting strangely and gives you a million volts of electricity in a bottle. I steal and feed it this bottle

It seems to be unharmed.... until it zaps you with a million volts of electricity. You are now not only a pile of ashes, but also an electrocuted pile of ashes. It burps rather rudely and spits out the bottle.

I feed it leather armor

The Mimic is incredibly pleased by this sustenance, since leather is an animal product... Almost as good as the ham sandwich it had when this forum was first created so excited in fact that it spits out Leather Armor +1, then opens its mouth expectantly.

I feed it leather armor +1

The mimic  politely thanks you and points to a treasure room with two staffs of the magi.

I feed it a ton of elemental energy.

it pops into a light rain of common magical items that are purely cosmetic

i feed it Kirby.

The mimic has Vietnam flashbacks as kirby walks away.

I apologize to the mimic and give it a ice cream.

the mimic spits up a mimic, with a smaller mimic in that mimic's mouth, with a smaller mimic in that mimic's mouth with an arm holding a gun in that mimic's mouth. It asks for all your money.

I feed it a goat.

I calmly transform into a balor as the mimic spits out a goat of terror that obeys you.

I hand it a thousand gold coins.

It spits out an equal amount of platinum.

ifeed itpain

I use my longsword and cleave you. As the mimic considers go under a witness protection program.

I give it a Turkey.

It enjoys the turkey and licks your face like a puppy, expecting more, when it doesnt get more it eats your face off.... HOW LONG IS IT GONNA TAKE BEFORE PEOPLE LEARN NOT TO FEED WILD ANIMALS???

Anyways lol

I feed it a +1 ham sandwich with +2 rye bread, +3 mustard, cheddar cheese and mayonnaise of healing

it spits mayonnaise in your eye ,but also hands you twenty gold. 

I feed the mimic oak tree seeds. 

It spits out a dryad

i feed it gnormongond the world serapent 

The mimic looks at you and asks for something smaller.

After turn back to normal I cast hero's feast for the mimic.

The mimic gulps down the entire feast, and becomes HELLA SWOL!

I feed the mimic the fresh prince of bell hair.

The Mimic spits out some secondary actors from that TV serial.

I fed the mimic a bunch of Rodeo bulls.

The Mimic starts bucking around and saying howdy

I feed it A Sammich made with love

It spits out a Frodowich

I feed the mimic a bag of holding

The mimic is gone, sucked into the astral tear that forms as the bag is punctured. A new being forms, and as the new mimic opens it's mouth, a smaller mimic extends! This bizzare mimic chain extends out and bites the tip of your nose.

I feed the mimic Danny Devito.