Buzzigigas is a deity (large for Mudkeep characters' size) created by Buzz Lightyear's legs with Regigigas' arm sleeve and right arm. As it is only limbs, it can only attack with kicks and punches. The arm does the hitting whilst the legs do the running.
Mudkeep disposed of Buzz Lightyear and Regigigas' bodies after defeating them both and together in Stilioseland.
It is (somehow) brought back to life and fights back in Attempt.