Koko the Gorilla Mourns Her Friend, Robin Williams

Although the two met more than a decade ago, Robin Williams and Koko the Gorilla shared a special bond. ET is with Koko today as she continues to mourn the loss of her friend.

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"Koko has been really somber and low-key," said Koko's trainer Dr. Penny Patterson. "She's needing a lot of support."

Koko, 43, understands spoken English and uses over 1,000 signs to share her feelings and thoughts about daily events. She met Robin in 2001 in a video gone viral. According to Dr. Patterson Koko's "memory is strong" and she is aware of who it was that passed.

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"There's only one Robin that's ever been in our life," Dr. Patterson said.

According to Dr. Patterson, Robin once helped Koko get over a tough period in her life.

"What happened when Robin visited is that Koko was actually in mourning for her lifetime companion, Michael, and it was Robin who brought her out of it," said Dr. Patterson. "The first time she smiled after Michael passed was when Robin and her met."