When Robot and Monster discover Perry, a Mechanical co-worker of theirs, always seems to be smiling, Monster is distressed that he may no longer be "The Happiest Guy in the World". Robot takes it upon himself to help his friend regain his smile.
- Although Perry first appeared in Monster's Great Escape (cameo in the background), this is the first episode to mark him as a major character.
- This is the first time a musical number is performed.
- Monster's horns are shown to shift down when he's depressed.
- It is revealed that Perry's constant smiling is due to his facial gears being broken.
- This is the first time Perry's car has been ruined/destroyed. In this episode, Robot tears out his car's wiring, causing it to explode; the second time Robot vomited into its compartment in Game Boys; the third time Marf attacked it and it is run over by a steamroller with Perry still in it in How to Train Your Marf.
- Ogo is shown to be an expert in Gregorian chanting.
- Fourth wall break: At the end of the episode after Robot gets injured by his unhappy ray, Perry looks at the camera and says "That made me kind of happy".
- At the beginning of the episode, Gart said that Perry's car was towed away and destroyed. However, it is shown in a later scene when Robot tries to make Perry "unhappy" by taking his car's wiring out, suggesting that Perry ethier bailed it out so it could be fixed or bought a different one of the same color.
- Song: The Happiest Guy in the World.
- Perry had appeared in episodes before this, but in this episode, he was considered a new guy. It is possible that this episode has taken place before those episodes.
- The episode title is a reference to the old song of the same name.
Spitfire: (after seeing Perry's smile) Wow, he has a smile that lights up the whole room! Kind of makes me want to smack him!
Gart: Perry, your car has been towed, and destroyed. Your pets ran away, and your wife just called, she just doesn't love you anymore. Oh! And I accidently dropped hammer on your head. ("accidently" drops a hammer on Perry's head.)
Perry: Are you nuts?! I'm not happy! I'm MISERABLE!
Monster: But, you smile all the time.
Perry: (bangs against face screen) My face gears are broken! I can't stop SMILING! Do you know how horrible it is to LIVE LIKE THIS!?!
(after Robot gets injured)
Perry: (turns toward viewers) That made me kind of happy.
Monster - (Singing) I can't think of a happier fella! (sees Perry dancing and still smiling) Except for that guy. What the heck?