In-universe, it’s a good way to give Rent another set of abilities through a helper. It also helps some encounters more dynamic. It means that he’s never truly alone despite being “solo”.I can't say I'd understand why the author felt the need to develop a super rat in this story. My only guess is that the author has a rodent as a pet and instead of an author self-insert character, it's the author's pet insert.
Next up is "When am I?" and "Why am I?" and you got yourself the 5 W's.Who am I? What am I? Where am I? All good questions