A Spanish zoo keeper dressed in a gorilla suit was so convincing he was mistaken for the real thing and shot with a tranquilliser dart.
Employees at Loro Parque Zoo on the Spanish island of Tenerife were taking part in a drill to ensure they had an emergency plan in case one of the gorillas escaped from its enclosure.
One keeper drew the short straw in the exercise, and was made to wear the hairy ape costume and run around the park mimicking a gorilla.
Unfortunately, nobody thought to tell the vet about this aping around, so when he saw the escaped "gorilla" he sprang to action, and shot it with sedatives designed for a 180 kilogram primate, the Daily Mail reported.
The 35-year-old keepers was taken to the University Hospital of the Canary Islands where he was treated and discharged, the zoo said in a statement.
"As a matter of course, Loro Parque, like all zoos and animal parks, regularly carries out this kind of emergency drill," it said.
"These simulations are designed to guarantee security, emergency measures, and to train people who work in these enclosures."