The mimic has now relieved all of its minor aches, pains, inflammation, fever, headache, heartburn, stomachache, indigestion, acid reflux and hangovers, while neutralizing excess stomach acid.

I feed the mimic a grand piano made in 1874...

The mimic sings Debussy's Clair de Lune.

I feed the mimic a roll of toilet paper and a mask.

The mimic spits out germ-x as appreciation for the toilet paper and mask. You do not wanna be in that room with the mimic when it has no toilet paper. 

I feed the mimic a copy of "maneater" by Hall and Oates. 

(( Btw, you didn't specify if the copy was a digitalized one or simply a plagiated version ))

The Mimic don't understand how it works an illusory image of a Human person.

I feed the Mimic all the members from The Cult of the Dead Cow.

The mimic spits out a dead cow and the cows' organs. They udderly stink. The joke too.

I throw in a pot of beans seasoned with the remains of the rest of my party.

The mimic looks sad at the pot, because everyone forgot it’s birthday yesterday. 😢

To make up for it, I put a party hat on the mimic and everyone else, get confetti shooters and presents, and feed it a large birthday cake

The Mimic starts being dizzy after he/she looks (( it's unclear the gender they have..... aughh )) at the fireworks blasting on the room.

I feed the Mimic a barrel of Champaign, EXTRA quality ( from my lands ).

The Mimic eats the barrel, spitting out the champagne. It then sings La Cucaracha 4 times.

I feed the mimic a diamond in the shape of a steak.

The mimic grows diamond teeth. 

I feed the mimic slim fast. 

The mimic downs the slim fast like its at a frat party, then spits up an iron ring. This ring gives you SR15 but is cursed with spell absorption & a taste for blood, only learned after you adorn the ring.

I toss in a portable-hole-in-a-sack trap

The portable hole-in-a-sack trap fails to work due to the rough digestive acids inside the Mimic.

I feed the mimic a sack of Concrete, ( extra quality ).

The mimic becomes much much heavier. Like it wasn't heavy enough... Anyone it jumps on will get turned into meat juice. 

I feed the mimic a ultra marines chainsword.

It spits some Orcs groanning for moar weapons.

I feed the Mimic a ton of Mayonnaise.

It swallows mayonnaise.

I feed it an ultra marine bolt rifle (bolter).

It spits out a word bearers heavy bolter

I feed the mimic the book of vile darkness

It spits out a bible

i feed it a warp fire bolter, the superior form of bolt weaponry *laughs in tzeentch*

It spits out a blight launcher *Laughs in nurgle*

I feed the mimic the soul of slaanesh (if he/she/it has one?)

The gains some of slaanesh's 'freaky hobbies'... also the mimic now lays claim to the souls of unprotected eldar. Some noise marines come and play some heavy metal in the name of their new overlord ,and things get real crazy. 

I feed the mimic Pentiums

It spits Bytes and bits........

I feed the Mymic a RedHat                                                 

The mimic spits out... an old trench coat and a galosh!

i feed it a slice of cheese