Muscles Gator is the name given to a small anthropomorphic plush alligator sometimes seen on the stream. His name is derived from the pose he's in (flexing his arms) as well as his yellow tank top with a barbell on it that simply reads "MUSCLES". He is a Dakin plush manufactured in 1983. Whenever Muscles is on camera he is usually sitting on a shelf in the background or next to the microphone on the table.
Muscles is normally just used for decoration but has a minor following with fans of the stream who've imagined him as a sort of "muscle fur" character. He is seen as a goofy meathead who is obsessed with fitness and working out, but is a lovable "gym bro" who would be more than happy to let you borrow his weights or share his protein shake recipes with you... if you can beat him in arm wrestling. He's not the sharpest knife in the drawer but he means well and has a heart of gold.
Muscles was eventually given his own emote, "GBmuscles", a small full-body icon showing off his signature flexing pose. In 2018 a replica of his yellow "MUSCLES" tank top was made available in T-shirt form through the Gatorbox store.