Reggie is a male chimpanzee with brown fur.
Sometimes he wears a white and blue space suit while training for the space-shuttle mission. As the shorter version of the Space Ape, Reggie wore a costume similar to Janet's larger versions.
Reggie is a trickster, but his tricks are often harmless. He does what he is told and is trained to do. This made it easy for Janet to make him wear the small Space Ape costume.
What's New, Scooby-Doo?
Mystery Inc. come across Janet near the Centrifugal Force Machine getting Reggie ready for the next shuttle launch. When Velma asked who Reggie was, Janet opened the cockpit to reveal the chimpanzee. He approached Scooby, who backs into a pool while Reggie chuckles with delight.
Reggie was present during the evaluation of the mystery. Janet had trained Reggie to wear the smaller Space Ape costume to give the allusion that the alien was continuously growing. While Velma explained this, Reggie wrestles with Scooby for the Space Ape costume nearby. When the Space Ape 'reappeared', Reggie took off the mask to reveal that it was Scooby playing a joke.