Mascot

Mascots are a group of cosmetics that appear as a sort of companion to the class that they are equipped on. They are sometimes also referred to as pets, and some are referred to in-game as Pocket Buddies, along with other things.
When players equipped with a mascot kill an enemy unassisted by another player, the killfeed shows everyone in Pyroland that said mascot gets the assist, with its custom name if it has one.

Table of cosmetics that fit this category is in progress