When Koko the gorilla used the American sign language gesture for pain and pointed to her mouth, 12 specialists, including three dentists, sprang into action.
The result? Her first full medical examination in about 20 years, an extracted tooth and a clean bill of health.
Last month, Koko, a 135kg-plus ape, who became famous for mastering more than 1000 signs, began telling handlers at the Gorilla Foundation in Woodside she was in pain.
They constructed a pain chart, offering Koko a scale from one to 10. When Koko started pointing to nine or 10 too often, a dental appointment was made.
And because anaesthesia would be involved, her handlers used the opportunity to give Koko a head-to-toe examination.
"She's quite articulate," volunteer Johnpaul Slater said. "She'll tell us how bad she's feeling, how bad the pain is. It looked like it was time to do something."
Twelve specialists - a Stanford cardiologist, three anaesthesiologists, three dentists, an ear and throat specialist, two veterinarians, a gastroenterologist and a gynaecologist - volunteered to help.
"It's not often that we get to work on a celebrity," said Dr David Liang, assistant professor of medicine at Stanford.
The team set up shop at her "apartment", which looks like a remodelled box car, complete with a makeshift toilet, TV, DVD player and toys.
After four hours of tests - including a colonoscopy, gynaecological exam, dental work, X-rays, and ultrasounds - doctors pronounced her fit.
Koko, who on July 4 celebrated her 33rd birthday, was due for a checkup. While gorillas in captivity are known to live into their 50s, they are susceptible to heart disease and a thickening of the arteries.
Koko and Ndume, her partner of 11 years, have been trying unsuccessfully for a baby, and the doctors thought the checkup could let them know whether she had any biological problems preventing it. She doesn't.
Her teacher, Francine Patterson, was at her side when the anaesthesiologist prepared to put her under.
The Gorilla Foundation has studied gorilla intelligence by teaching American Sign Language to Koko and another gorilla, Michael, who died in 2000.