ThunderCats (1985)

S2E18 The Sound Stones

Feeling unappreciated and restless, the Thunderkittens decide to leave home but soon face trouble after getting sick from some berries they ate. Luckily, a creature named Cudi comes to their rescue. When the other Thundercats locate the Thunderkittens, they invite Cudi to join them at Cats Lair. However, Mumm-Ra has been watching and takes on Cudi's appearance to infiltrate the Lair. Chaos ensues, and the false Cudi locks the Thundercats in the council chamber. Realizing it's Mumm-Ra in disguise, they manage to break free and ultimately defeat him.