Deku always wanted a puppy, but his mom couldn't afford to raise him and a dog.

Deku is a Slytherin (but a good one) and his patroness is a Welsh Terrier.

Deku once had a pet fish until Bakugou's cat ate it

Bakugou has an outdoor cat with the same attitude as him and his mom. The cat is named Satan.

Bakugou doesn't let anyone in his room cause he has a picture of his family, and doesn't want to be called a softie.

Bakugou's favorite kind of books/movie are thrillers/mystery, so he can try to solve the issue before the characters.

Todoroki never had pets since his father said it would take time away from his training.

Todoroki asks Kouda to hold his rabbit, since he doesn't like people hugging him.

Todoroki's mom taught him how to play the piano when he was younger, before his father's training.

Iida has a family grey hound, named Maximum. Raw fed, one hour exercise routine, and fake glasses that matches Tenya's.

Maximum later became a service animal for Tensei, trained by Tenya himself for both Tensei and for a school project.

Though Tenya did not get his brother's chill personality, he did get his rock/metal music taste.