Full Moon is an episode of Hey Arnold!.
Harold, Sid and Stinky moon Principal Wartz, but Arnold is blamed, even though he was just an innocent bystander.
Arnold is walking to class when he sees Harold, Sid, and Stinky at the corner. They plan to moon Principal Wartz. They ask Arnold if he wants to join in, but he thinks it's not a good idea. The three tell him he just doesn't have any guts.
Wartz leaves his office and starts walking toward them. Harold, Stinky and Sid wear masks to disguise themselves. Wartz walks by and they unbuckle and unzip their jeans fully exposing their butts. Wartz puts on his glasses and is shocked. The boys run away laughing while Wartz tries to stop them. However, they get away and Wartz takes Arnold to his office, unaware that Harold, Stinky and Sid are the culprits.
Arnold says he didn't do anything, but Wartz says he did see who did it, which Arnold agrees. Wartz asks Arnold who did it, but Arnold won't tell because he's not a snitch. Wartz assigns Arnold four weeks detention for failure to cooperate. Arnold leaves while Wartz makes a phone call. Sid, Harold, and Stinky arrive and ask Arnold if he snitched. Arnold says he didn't, which the boys are happy about. Arnold tells them Wartz gave him four weeks detention, but Stinky says he didn't even do anything.
Sid and Stinky, feeling guilty think about telling Wartz the truth, but Harold, determined to stay out of trouble, refuses, saying Arnold getting caught is his fault, depite him not participating in the prank. Throughout the next four weeks, Arnold goes through many punishments, but still refuses to tell who did it, even when Wartz threatens to mark his permanent record, still unaware that Harold, Stinky and Sid are the culprits. Harold asks why Arnold didn't admit, and he says because he's not a snitch. That night Harold is sleeping but is having guilt. The next day, Wartz prepares to mark Arnold's permanent record, when suddenly Harold, Sid, & Stinky burst in admitting in tears confessing that they were the culprits and Arnold had nothing to do with it.
Wartz, who finally discovers the truth lets Arnold off the hook (for now). The boys say Arnold has guts. They plan on pulling another prank and try talking Arnold into it.
- This was the first episode produced using digital ink and paint instead of cel animation.
- This episode takes place during the month of April.
- This is the second time Arnold gets detention. The first was in the episode "Girl Trouble". In both episodes, Arnold gets in trouble for something that wasn't his fault.
- Principal Wartz has a poster advertising the Woodstock Festival in his office.
- In this episode, it is revealed that Harold has a mole on his right butt cheek. This can be seen during the very quick glance of his butt when he moons Principal Wartz.
- Wartz revealed that as a kid, he squealed to the teacher about a prank his classmates pulled. As a result, he was given a gold star, but became hated by his classmates.
- He also mentions his reputation as a snitch in elementary school followed him through high school and even college; he didn't even have a date until he was 23 years-old.
- The episode was ranked #75 during "Top 100 Greatest Moments In Nicktoon History".
- During the confession scene, Vesti la giuba from Pagliacci is heard.
- The animal mouth masks that Harold, Stinky, and Sid are wearing to moon Wartz is a goose, a pig, and an owl.