In addition to many millions of humans, at least one other primate is likely mourning the loss of actor and comedian Robin Williams today. Koko, the gorilla who communicates in a modified version of American Sign Language and is said to understand even some spoken words, filmed an ad campaign with Williams in 2004 to raise awareness of threats against gorillas. The video below shows their first meeting, where Koko asks Williams to chase and tickle her, steals his sunglasses, and rummages through his wallet.