In An Instant (2015)

S6E16 Fred Goes Ape

After a mix-up at the pharmacy, Fred accidentally gets his hands on pills that transform him into an ape. Barney witnesses this bizarre occurrence, prompting him to question his own well-being. However, when the two fathers take their children to the zoo, Fred inadvertently ends up in the monkey enclosure after swallowing another pill, revealing his predicament to everyone around.