Robin Williams will always be remember for his comic brilliance. He was known to be a personally empathetic person. You can see it in many of his roles, and with his interactions with Koko the noted lowland gorilla who communicates with sign language.
In 2001, Williams met Koko for the first time. The Gorilla Foundation posted video of their meeting.
The Foundation indicated when Koko learned of Williams' passing he became very somber, bowed and her lip quivering. The wording of the press release asks the public to remember Williams as one of the most powerful ambassadors of ape conservation. The actor's meeting with Koko has certainly made an impact - it's being called charming and incredibly moving.
According to The Gorilla Foundation, Williams tickled Koko and made her smile for the first time in months since she'd lost her gorilla companion, Michael. The meeting stuck with Williams - he'd talk about Koko in his stand-up routines and spoke about her on "Ellen."
You can watch the full video of Robin and Koko's meeting here.