The Flintstones S06 E16 Fred Goes Ape

"Yabba Dabba Doo!"

A mix-up at the pharmacy gives Fred pills that turn him into an ape. Barney is the only one to see this short-lived effect, which makes him wonder about his own health. But when the two dads take their kids to the zoo and Fred ends up in the monkey cage after taking another pill, his problem becomes apparent to all.