AU where Tobias gets stuck as his cat Dude instead of a hawk and lives in Jake's house
Okay, I'm gonna preface this with a note that all of my Animorphs knowledge comes from people blogging about it and a single reading of the ant book six years ago, so stuff here may be incorrect or inaccurate to canon. Sorry!
At first, they try keeping Tobias secret. He stays in Jake's bedroom, comes in and out the window, hides if he hears anyone coming, and so on. It's a pretty good plan, they think, it'll will work for a while.
It works for all of three days. I'm not sure what exactly causes it to fail but someone finds out Jake is keeping a cat in his bedroom and there is a conversation around the dinner table about it.
Honestly, I'm not sure how Jake convinces his parents to let him keep the cat, but he does it /somehow/. So Tobias gets to stay. The argument that Homer doesn't seem to mind him is possibly used at some point
The Animorphs all discuss what Tobias's "cover" name should be. Nobody wants to risk suspicion with a cat named after a missing classmate so a lot of names are thrown around.
It ends up just being Cat. Tobias is essentially undercover as Cat the cat. He is not amused.
Not having an eye-in-the-sky constantly without someone morphing does make some things more complicated, but Tobias is able to do stuff as a cat too. It's most likely easier to deflect suspicion about odd behaviour as a cat because everyone generally accepts that Cats Are Weird
That's all I've got. I'm sorry this isn't up to my usual standards :(I just don't know Animorphs well enough to go as over the top and in-depth as I'd like to.