‘The animated sequences of Forbidden Planet, especially the attack of the “Id Monster”, were created by the veteran animator Joshua Meador, who was loaned out to MGM by Walt Disney Pictures. According to a “Behind the Scenes” featurette on the film’s DVD, a close look at the creature shows it to have a small goatee beard, suggesting its connection to Dr. Morbius, the only character with this physical feature; the bellowing, now visible Id monster, caught in the crewman’s high-energy beams during the attack, is a direct reference to and visual pun on MGM’s familiar roaring mascot Leo the Lion, seen at the very beginning of Forbidden Planet and the studio’s other films of the era.’

Thank you wikipedia.