Tracy the Gorilla was the third member in both the teams,The Ghost Busters and the Ghostbusters.
Tracy is a genius-like gorilla who figures often out how to get the Ghost Busters out of a sticky situation, probably explaining why he carries the bag containing all their gear. He can't speak, usually forcing him to convey his intentions via drawing or an impromptu game of charades with his friends.
In the sequel series it's revealed Tracy actually invented some of their newest anti-ghost gadgets. Tracy also displays superhuman strength, up to lifting and throwing a replica of the Statue of Liberty into the ocean with his bare hands. He can also speak snippets of English, usually a grunted "Okie dokie!" when the Ghostbusters ask for his help. The primary humor of the series was slapstick, with scenes centered on the perpetual bumbling of the characters, good and evil alike. The series also made references to classic cinema; the names "Spencer" and "Tracy" were taken from the famous actor Spencer Tracy, while the name Kong – ironically not given to the gorilla – was a clear homage to King Kong.