Once every seven years of the seventh month, the moon goes through a rainbow-coloured phase, or as Doc puts it, a "triple coloured moon all the way." The 7D head to Starchbottom's cabin in the woods to witness this cosmic event. Unfortunately, when the moon does change colour, the 7D undergo different transformations, including Happy and Grumpy.
This episode has the following tropes
- Arc Words:
- "Something happens to me when the moon turns [insert specific colour]. I transform, I change, into something so unspeakingly awful that no one is safe from me!". This is said when we learn that the 7D undergo different transformations under the light of whatever colour the moon changes into.
- "X all the way!" Doc says this whenever he comes close to proving his moon theory.
- Breaking the Fourth Wall: The 7D reveal to the viewers that they go through different transformations under a certain coloured moon. Also at some point in the episode, Grumpy cues the camera to zoom in on him when revealing that he will undergo a transformation under the blue moon.
- Brick Joke: Grumpy mentions that he was feeling ferblodgety when he tries to get out of going to observe the triple-coloured moon. It later gets brought up again by Sneezy.
- By "No", I Mean "Yes": After Sleepy encounters Grumpy under the effects of the blue moon.Sleepy: It was Grumpy, but it wasn't! It was horrible! It was like he cared about me!
- Call-Back: While under the effects of the blue moon, Grumpy sports the same creepy smile that was shown back in "Oh Happy Grumpy".
- The Cameo: Queen Delightful makes a brief appearance when she wishes Starchbottom good luck on his weekend vacation.
- Calling Your Nausea: How Grumpy tries to get out of going to see the triple-coloured moon. He claims that he's feeling a little "ferblodgety".The 7D (sans Happy): Ferblodgety? Ewww!
- Cassandra Truth: Several times.
- When Doc theorizes that a triple-coloured moon will occur, he was laughed out of the academy. That is until he proved them wrong at the end of the episode.
- Whenever one of 7D encounters Happy or Grumpy who have turned into monsters, they would report the situation to Doc, but the moon will get blocked out by some dark clouds, so when he goes to investigate, he'll only see them being their usual selves.
- Comical Overreacting: Happy, Bashful and Sleepy (and then later on Dopey and Sneezy) all react in terror when they had an encounter with Grumpy under the effects of the blue moon.
- Crazy-Prepared: When Doc thinks he forgot the key to the cabin, the rest of the 7D back him up with spare keys.
- Creepy Doll: Sneezy becomes one under the light of the indigo moon.
- Cue the Falling Object: Or rather "Cue the Breaking Object". When Happy learns, to his horror, that the moon will turn red first, his guitar string snaps.
- Didn't Think This Through: Happy and Grumpy's solution to hiding from everyone so that their personal nightmares are over? Hide out in Starchbottom's cabin, which happens to be the very same place that Doc is heading to observe the moon. Also, they didn't think to hide out in a room with no windows, since every time the coloured moon is blocked, they instantly revert back to normal.
- Explain, Explain... Oh, Crap!: Starchbottom has this reaction when he realizes the key to the bait shop (which holds the key to the boathouse) is back in Jollywood, much to his dismay.
- Face-Revealing Turn: When Bashful encounters Grumpy (who undergoes a personality change under the blue moon), the latter slowly turns to the former, revealing his very creepy smile.
- Failed a Spot Check: Grumpy doesn't seem to realize that the monster he encountered is Happy, since the monster is wearing his vest, hat and pants.
- When Happy starts to transform, Grumpy, Dopey and Sneezy didn't see that his hand has grown claws.
- Faux Horrific: Lanyards, apparently.
- Foreshadowing: During the flashback, when Starchy gives the 5D the spare keys to the cabin, if you look closely at the Split Screen, it's shown in five colours (indigo, orange, green, yellow and violet), and when Strachbottom says each of their names, each dwarf appears in place of that colour. Then later on, it's revealed that the rest of the 7D also go through different transformations.
- Got Volunteered: After Happy tells the others about Grumpy becoming a monster (or as he puts it "Were-Grumpy"), Sneezy pushes Bashful downstairs, not wanting to encounter a "Were-Grumpy".Sneezy: (to Bashful) Your turn.
- Hulking Out: Bashful under the light of an orange moon, complete with Hulk Speak.
- Irony: Happy and Grumpy fled to Starchy's cabin to avoid the rest of the 7D so that they wouldn't scare them. Turns out the rest of the 7D also went to the cabin to watch the moon change colours and they end up seeing Happy and Grumpy's transformations.
- Jaw Drop: Dopey does this upon encountering "Were-Grumpy".
- Klatchian Coffee: Sleepy becomes a coffee-loving crazed lunatic under the effects of a yellow moon.
- Limited Wardrobe: Discussed and Lampshaded. When Happy's transformation starts up again:Happy: (while pushing Grumpy, Dopey and Sneezy out of the room) Go away, I'm changing!Sneezy: Why? You always wear the same thing.
- Losing Your Head: Sneezy and Dopey become so terrified of Happy's werewolf-like appearance that their heads immediately pop right off. Also when they do, they kept tossing their heads to each other before putting them back on.
- Lunacy: All of the 7D go through different transformations under a specifically-coloured moon.
- Mass "Oh, Crap!":
- Whenever the 7D (sans Doc) encounters a transformed Happy or Grumpy.
- The rest of the 7D when they realize that they're going to transform under the rainbow moon.
- Midnight Snack: Grumpy decides to have a nighttime snack before the blue moon occurs.
- Nested Mouths: Played for Laughs. When Grumpy encounters Happy under the effects of the red moon, he screams so hard that his own tongue screams out another tongue.
- The Nicknamer: While under the effects of the blue moon, Grumpy gives several nicknames to his friends.
- Noodle Incident: Dopey ate the map on the way to the cabin, causing Doc to get lost.
- Now You Tell Me: We later learn that when the rainbow moon occurs, the rest of the 7D transform into monsters (not just Happy and Grumpy).
- Oh, Crap!: Several of these occur.
- One Crazy Night: Doc wants to observe a natural phenomenon called the "Triple-coloured moon". Doesn't sound so bad right? Unfortunately, when the moon does change colour the 7D undergo different transformations making this a crazy night.
- Our Centaurs Are Different: Dopey turns into a goat-centaur hybrid under a green moon.
- Our Werewolves Are Different: Under a red moon, Happy turns into a werewolf-like creature.
- Pun-Based Title: Once in a Purple Moon (Once in a Blue Moon). Coincidentally, the term "once in a blue moon" means something that happens very rarely, like with the triple-coloured moon.
- Running Gag: Any time when Grumpy or Happy transform.
- Scream Discretion Shot: The rest of 7D scream "no" (along with Bashful shrieking), when they start to transform under the rainbow moon.
- Shout-Out: Happy's werewolf-esque Transformation sequence is similar to the iconic scene of David transforming in An American Werewolf in London.
- Speak in Unison: This happens when Sneezy finds Grumpy and Happy hiding out in the cabin.What are you doing here? Waiting for the moon to change colour.
- Strange Minds Think Alike: The 7D and Starchbottom all decide to head to the latter's cabin in the woods, mainly because 1) Happy and Grumpy want to hide from the world until the triple-coloured moon phenomenon is over, 2) Doc planned on going there to observe the moon and 3) Starchy wanted to spend his weekend off there.
- Talking in Your Sleep: Sleepy does this when conversing with a transformed Grumpy.
- Tempting Fate:Happy: ♫ Triple-coloured moon/ Shining overhead /Hope I get to see you /But I hope you don't turn red. ♫Doc: Funny you should mention that Happy. In the first phase, the moon will turn red!
- This Is Gonna Suck: This is Starchy's reaction when he realizes that he has to go all the way back to Jollywood to get the key to the Bait Shop.
- Transformation Sequence: Happy is the only one where we see him transform. Any time the others transform, it's offscreen.
- Visual Pun: A literal blue moon occurs in this episode.
- Wild Take: Several of these occur.
- Worth It: Despite being turned into an idiot under the light of the rainbow moon, Doc is ecstatic when he proves the academy wrong about his triple-coloured moon theory.
