Updated: Oct. 16, 2015.

No one can resist a box full of kittens -- not even a gorilla.

Koko, the famous gorilla who can "speak" via a sign language vocabulary of more than 1,000 words, loves babies and kittens. And for her 44th birthday over the summer, caregivers at the Gorilla Foundation in California arranged for Koko to spend some time with a box full of kittens.

Video from the party was released this week, much to the Internet's delight. At one point, Koko uses her sign language to ask that a kitten be placed on her head.

But what really made the birthday special for Koko was that she was allowed to keep two of the kittens, Ms. Gray (the one on her head) and Ms. Black.

The rest were adopted by humans.

"With Koko’s new kitten adoptions, she couldn't be happier," the organization wrote in a newsletter. "She is signing more than ever."

Koko has had several cats as pets over the years, including a gray kitten named All Ball. When All Ball got outside of the cage and was hit by a car just six months later, Koko grieved by using the signs for "cry," "frown," "sad" and "trouble."

The gorilla's relationship with her kitten became the subject of the children's book, "Koko's Kitten." The foundation wrote that Koko's relationship with her new cats could become a multimedia sequel to "Koko's Kitten."

Koko made headlines last year when she mourned the loss of Robin Williams, who had not only visited her but got a smile out of the gorilla at a time when she was sad over the death of her companion.

However, not everyone supports the idea of gorillas being held in captivity, and some have questioned Koko’s treatment specifically. Her diet and overall quality of care have drawn criticism, though the foundations say its choices are approved by a veterinarian, according to Slate. Read more here and see how to protect the gorillas worldwide at WWF.

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