Gilligan's Monkey was a small Capuchin monkey he had befriended on the island. It is not known if was native to the island or if it was left behind by Dr. Balingkoff, who owned a similar Capuchin monkey as a pet on his last trip. The nameless monkey had a habit of imitating Gilligan; when he lifted a crate of lost plastic explosives, it lifted a small log. It was also very mischievous; setting off explosions with the plastic to amuse itself and almost blowing itself up in the process, but luckily, the Skipper caught it after it was thrown clear in the explosion of the Girl's Hut.
- Other primates on the island include Gladys, The Gorilla and an orangutan (mistaken as a gorilla) that abducts Tongo the Ape Man.
- The various animals on the series were possibly provided by Frank Inn, the owner of Benji, who also supplied animals to "The Beverly Hillbillies," but this is unconfirmed.