Arthur’s pet hamster - Galahad (While that is his “legal” name, he is more commonly referred to as “Galaham”)
Galahad was born with a condition that left his lower half paralyzed. With Arthur’s mechanical know-how, he built the little guy some fancy new wheels that allowed him to move about to a surprising degree.
Arthur regards him to be his tiny assistant, though his aptitude at mechanics and robotics are questionable (at best). He doesn’t let that get in his way though and will tinker with random objects when no one else is looking.
Whenever something just randomly falls apart at Kingsmens Mechanics, odds are you’ll find Galaham nearby with cheeks stuffed with screws and bolts.