He-Man and the Masters of the Universe - Season 1 Episode 15 Prince Adam No More

Angered by his continual defeats, Skeletor blames Beast Man, banishing him from Snake Mountain and his evil forces. Meanwhile, King Randor is preparing for a Royal tour of Eternia, accompanied by Man-At-Arms and a guard of his choice. The King chooses He-Man, but Adam, upset that he always has to play down his qualities to hide his alter-ego, convinces the King to choose him instead. Beast Man spots the touring party, and aided by his Shadow People followers, he ambushes them. Determined to prove his worth to his father, Adam resists transforming into He-Man and instead tries to stop the attack as himself, but he is overpowered, and Beast Man captures Randor, intending to use his capture to win his way back into Skeletor's good books...