Steve Rogers-
The two of you saved up your money an adopted a German Shepherd puppy.

Tony Stark-
You asked Tony if he'd like to adopt a pet with you, and he was hesitant about the idea. So you compromised, and got a pet. An adorable little leopard gecko.

Bruce Banner-
You had planned on getting a kitten from the animal shelter, but an older cat stuck out to you and immediately you both knew that this cat was meant to come home with you.

Clint Barton-
It took a lot of convincing, but finally Clint agreed to let you bring home two baby dwarf goats.

Thor Odinson-
Growing up, you always wanted a Great Dane. You expressed this interest to Thor once, and with a little help from Tony, he surprised you with a Great Dane for your birthday.

Loki Laufeyson-
Loki took you to Midgard once and while you were there, you went into a pet store. Midgardian animals fascinated you, so Loki bought you a ferret.

Bucky Barnes-
You wanted Bucky to have someone there to comfort him while you were gone on missions, so the two of you went to the animal shelter together and adopted a sweet dog.

Pietro Maximoff-
You thought it would be a little ironic if you and Pietro adopted a turtle, considering the fact that he was a speedster.

Peter Parker-
You hadn't planned on getting a pet, but the two of you went into the pet store one day and fell in love with this little rabbit.

Peter Quill-
Black markets on other planets often sell exotic animals, and one day you spotted a familiar animal from earth and knew you had to rescue it. Peter quickly warmed up to the tiny kitten.

Sam Wilson-
Sometimes you tease him by calling him 'bird boy' so what better pet to get then a bird? Make that two birds.