SpongeBob SquarePants (1999)

S1E22 MuscleBob BuffPants

SpongeBob believes that becoming fit will earn him more admiration. However, he quickly realizes that working out is tougher than he anticipated. To boost his image, he orders "anchor arms," which he fills with air to appear muscular. His deception is soon exposed when Sandy enters him into the annual anchor toss contest at Muscle Beach, revealing the truth about his inflated appearance.