Koko liked to make jokes. She enjoyed the reaction they would get. In the first clip Penny reads Koko a card that was sent in by some children. They want to know if Koko has a middle name. Koko responds to the question by signing that her middle name is “devil.” Koko could certainly be a little devil at times, expressing her contrarian and mischievous side.
Later, Koko calls Penny a “gorilla,” then Koko rushes off for a game of tickle chase - cause that’s what gorillas do.
Note that only Gorilla Foundation founders Penny and Ron went inside with Koko throughout her life, as they were present with her from the age of 1. All other gorilla caregivers remained outside the mesh and communicated with Koko via sign language and spoken English.
Video Credits: Filmed by Dr. Ronald Cohn, Gorilla Foundation co-founder, 1990 (Koko at age 19). From videos 413 and 426 of the Koko Archive (KokoArc).