It spits out a magical chain of infinite bag.

I feed it vecna's hand and eye.

 Well I guess one of us has to change. 

The mimic eats the hand and eye and waits expectantly for a head, but after a moment it spits out a dracolich.

I feed the mimic the last guardian.

The mimic spits out some last guardian action figures siting on top of a sculpture representing your hopes and dreams (the base of which had RIP carved into it).

I feed the mimic a copy of Jet Grind Radio/ Jet Set Radio (Dreamcast), Jet Set Radio Future (Original X-box), Ollie King (Arcade Machine), and their respective soundtracks. 

The mimic eats the collection and spits out two pairs of totally bodacious shades. One pair you, another for itself.

I feed the mimic a piece of pie in a paper cup, the ultimate road food!

The mimic slurps up the pie, cup and all. It spits out a treasure map to the greatest roadside diner and looks expectantly at your car. 

I feed the mimic my law school applications. 

The mimic chokes down the applications and spits up a heaping pile of debt and a state bar license. It hopes you can help it out if it ever gets in a jam.

I feed the mimic my many unanswered job applications.

the mimic spits out a few news paper clippings of local jobs that fit your qualifications, and personality. 

I feed the mimic some mexican hot chocolate ice cream in a waffle cone (dark chocolate icecream with chunks of chocolate, and a bunch of small bits of hot peppers mixed in)... fire and ice in the form of food.

The mimic shakes and gurgles as if it had its first case of heartburn and brain freeze at the same time.  The mimic spits out a potion bottle of pink liquid which the label reads "Pepto Bismal".

I feed the mimic all my wholey socks that no longer have a match.

The mimic spits out pairs of socks, joy for you. I feed the mimic my old character sheets.

The mimic just laughs.

I feed the mimic poptarts.

Time starts to go backward, until the mimic was born. it then goes to valhalla for some reason.

Kathra then feeds it a dagger.

The mimic instantly grows spiky bits all over its lid and sides. It then cackles in a rather frightening way. The creature is looking markedly more menacing than before.

I feed the mimic a catnip mouse.

The mimic bounces around the room wildly.

I feed the mimic a bottle of soju!

The mimic begins spouting random bits of Korean, as it continues to bounce around the room. It's movements become more erratic, until it finally trips over the piles of debris from past gifts. At first it seems to be knocked out, but then you hear a snore. From out of its mouth tumbles a saliva-coated Korean-English dictionary that smells vaguely of Gnome feet. The mimic does not seem to notice and sleeps peacefully on.

I  feed the mimic the complete works of William Shakespeare.

The mimic spits out the Latin grammar school curriculum of Ancient Greek and Roman plays that Shakespeare had to study in grammar school as a kid as a how-to for writing like Shakespeare. 

I feed the mimic the collected works of Euripides and Titus Maccius Plautus. 

The mimic eats them. And gets too bored, falls asleep.

I crank open its mouth and feed it a Devastation Orb of Fire.

Do to your lack of imagination and general laziness of mimic gifts, the mimic spits it back in your face you take 2d12 fire damage.

I feed the mimic the Dark Souls board game and Kingdom Death Monster board game.

The mimic devours both board games and stops to contemplate for a while.

After a few moments the mimic throws up every rulebook from all editions of D&D signed by both Gary Gygax and Dave Arneson.

I feed the mimic my epilepsy medicine

the mimic seems a little loopy but unaffected.

I feed the mimic ice.