These are Jett's pets~
[note only one one of them is canon.]

In order on the picture they are:

Kyle (Koala) Charlie (Dingo)
Ava (Crocodile) Millie (Nankeen Kestrel)
Henry (Woma Python)

[this is more headcanon type stuff]

Kyle is his little buddy that he takes everywhere with him. He isn't fond of most anyone or anything but there are few exceptions...

Charlie likes to roam around and is the type to beg for scraps but has a bit of pride, he won't beg from strangers. He hangs around in Jett's yard a lot, though wanders from time to time but always comes back.

Ava is a young Crocodile that Jett owns. She usually just stares and observes, hardly ever moving at all unless necessary. She is still learning about the world around her.

Henry is Jett's pet Python, who he keeps in a locked cage when others are over at his house as he knows not everyone is as comfortable around such animals as he is. Henry is an active snake, always roaming around his cage, and almost never refuses a meal.

Millie is Jett's Nankeen Kestrel. She is a means to carry messages to others. Though, as with all of nature's animals, Jett treats her as more than just a tool. For that is not what she is. In fact she has her own room at his home, albeit a small one compared to all the others, it is linked to a window where she may occasionally go out and fly around an enclosure made for her that sits just outside the window.