The mimic gobbles up the McChicken greedily, then after several moments he spits out a McRib

I feed the mimic my old left hand that I don't need any more since I cut it off to replace it with... a better one. (now if I can just find a new eye...)

The mimic happily takes the hand and in return spits out a rabbits foot into your eye socket.

I feed the mimic cockroaches.

The mimic chomps down on the cockroaches and then proceeds to vomit up a gigantic urinal cake. Maybe you can use it to save the community garden... somehow...

I feed the mimic a home-roasted batch of delicious Bolivian pour-over coffee.

The mimic noisily slurps all the coffee and spits out a magical hipster finger mustache tattoo 

i feed the mimic a set of custom power ranger L.e.d. Nipple pasties 

The mimic doesn't eat the nipple pasties, it puts them on its... rivets? It does a twirling dance and makes itself sick then vomits up its entire contents. 

I feed the mimic some saltines and tonic.

The mimic relishes in the moment of a calm belly. But with wide-eyed fear, another heave sets forth a tiny baby wyvern.

I feed the mimic some tums.

The mimic ingests them the wrong way and begins vomiting. Among the vomit is the mashed up tums and everything the mimic has been fed so far.

I feed the mimic a kitten covered in honey.

The kitten quickly gets stuck in between the mimics teeth. Due to the honey, it can not get good purchase with it's tongue and we are now left with witnesses death and slow decimation of this kitten.

I feed the mimic some timber.

The timber feeds into the mimic like a wood chipper, sound effects and all. It spits out a three piece suit made entirely out of flannel and a lifetime's supply of beard oil.

I feed the mimic HypeFox's hat.

The mimic goes full lumberjack and starts telling you the music you like was only cool 5 years before you ever heard of it.

I feed the mimic chamomile tea. 

The mimic falls asleep and tranquilly snores out 9000 platinum pieces (did you know European pagans once used chamomile in rituals and fetishes meant to give you luck with money? now you know). 

I feed the mimic a book on pre-Roman Europe. 

The mimic starts yammering on about how the socioeconomic status of the world at large is nothing but a steaming pile of garbage, and then proceeds to vomit up a steamingredients pile of garbage.

I feed the mimic the rest of my leftover Chinese food.

The mimic produces a pair of jade chopsticks.

I feed the mimic some old Dick Tracy novels, comics, and dvds (with the movies, and shows/ radio shows on cd)

The mimic spits out most of Western fantasy's canon since Tolkien. 

I feed the mimic small Sumerian statues. 

The mimic spits out over a dozen photo-cunieform tablets that appear, upon further inspection, to originate from a variety of sites including Uruk, Jemdet Nasr, Nippur, Eridu, ur, and Kish

I feed the mimic 2 chickens in chainmail, A few notebooks filled with notes and character sheets, a small effigy made from a mixture of hair from both my head and beard, a bicycle with only one pedal, a case of Milwaukee's Best, an old infantry combat manual, some fresh baked cookies, and a ledger stolen from a local merchant. 

The mimic starts a garage sale and spits out a 10 percent off coupon.

I feed the mimic a Sphere of Annihilation 

The mimic puts it in a large room where all the garbage is; so the garbage can be destroyed. The mimic gives you a mending wheel.

I demand all the things I never got from my previous things I fed the mimic with no reward.

The mimic devours @GreySky_GodoftheMachine whole and burps with immense satisfaction. 

I feed the mimic compliments and affection. 

(ha that was only a magic clone) The mimic spits out a valentine's day card that has the image of the mimic in it painted like a French girl.

I feed the mimic a magical bag of infinite chain.