Rats (Normal)

Representing Randomness, Rats has a special connection to Star Master. It almost like they're platonically met for each other due to their eccentric behavior. However, his origin is depressing.

Turns out that Rats was a direct result of Star losing her father. So, in a deserve attempt to save her from becoming any lonelier, Neuron Master split her up into two beings, Star Master and Rats. While the former is still grieving over her dad, the latter did try to cheer up by being as "weird" as usual. Eventually, these two starmates become pals. 

It's unknown why Rats had disappeared for so long, but if we had to guess, then it could be that he just needed to recharge his energy. After all, his randomness does drain his energy so often.