Spike is practicing flying with Twilight but is struggling with more complex maneuvers when Smolder comes along and points out that since a dragon's wings aren't feathered like a pegasus or alicorn's, dragon flying techniques are different. With Smolder's help, Spike's flying improves.
When Spike goes into town to give Smolder a thank-you gift for the flying lesson, a large fireball crashes in front of them. It turns out to be Sludge, a somewhat pudgy adult dragon, who has injured himself in his crash. Spike offers to help Sludge recuperate at Twilight's castle with the help of the Mane Six. While Sludge is reluctant to accept help from ponies, he nevertheless agrees to the help. Sludge makes a recovery, and while thanking everyone for their help shows amazement at how Spike has thrived in Ponyville. When Spike reveals he was orphaned as an egg, Sludge suddenly confesses that his arrival was no accident, and that he is Spike's father.
Sludge tells a tale of how Spike's mother was sent out to scout a new migration path, and Sludge had decided to go after her, taking Spike's unhatched egg with him, so they could be together as a family, but Sludge ended up captured by a group of dragon-hunters. Despite a few gaps in the story, Spike accepts it at face value, and is eager to bond with his newly-discovered father. Sludge doesn't take much interest in Spike's activities, though, and decides he needs to teach him how to be a "real" dragon.
Twilight is initially supportive of giving Spike the opportunity to express his inner dragonhood, but she becomes concerned when it starts to appear that Sludge is taking advantage of Spike. At the elder dragon's request, Spike has given up his room and creature comforts, and begun living in the outdoors, while Sludge enjoys the creature comforts himself. Spike, ready to do anything his "dad" says, dismisses Twilight's concerns as jealousy that he's found a real parent and doesn't need her anymore. Later, Smolder finds him outside, and points out the inconsistencies with what Sludge has been teaching Spike and her own experience in dragon culture, finally getting Spike to realize that he's been used.
Sludge next sees Spike packing up and preparing for them to move out of the castle for good, into a cave chosen by Smolder. When Sludge resists, insisting that Spike still needs to learn more about being a dragon, Spike insists he's learned enough and is ready for them to go. The sting operation set up by Spike and Smolder works, forcing Sludge to admit that he lied about being Spike's dad because he became accustomed to the luxuries of the castle and didn't want to give them up. Smolder is quick to deny Sludge's claim that it's what any dragon would've done. Sludge leaves; afterwards, Spike makes up with Twilight and reaffirms that as far as he's concerned, she's his real family.
- Aesop Amnesia: "Dragon Quest" examined Spike's conflict of identity between being a dragon and being a pony by having him join the dragon migration to learn how to be a "real" dragon. The episode ended with him realizing that who is he and what he is are not incompatible ideas, so he rejects the dragons he met because they were a bunch of Jerkasses, embraces the Mane Six as the only family he needs, and is proud of the good virtues and values he's learned living with ponies. In this episode, Spike has the exact same conflict and resolution, although he already starts with the knowledge that ponies are his family. It is only when Sludge is starting to question Spike's "dragonish-ness" presenting himself as his father, that Spike starts to think he needs to change.
- Appeal to Inherent Nature: After Sludge's trickery is revealed, he tries to defend himself by arguing that taking advantage of the gullible is just what dragons do. Smolder is prompt to call him out on this pretext.
- Armor-Piercing Response: When Twilight expresses how worried she is about Sludge taking advantage of the young dragon, Spike delivers one to her so strong that an X-ray of Twilight shows her heart breaking.Spike: Maybe you just don't like that I have a real parent now.
- Bad Liar: Sludge's lies are pretty obvious. The Mane Six poke holes in his story about Spike's origin as soon as he tells it, but Spike lets it all slide in the name of being with his "dad".
- Bad Samaritan: Sludge claims he'll take Spike under his wing in order to "teach" him to be a dragon. It's all meant to exploit Spike's better nature so Sludge can live in luxury.
- Broken Pedestal: After spending the episode with him father/son style, Spike soon loses all respect for Sludge when he admits that he's not really his dad.
- Spike's flying lessons from Twilight are reminiscent of those that Rainbow gave Twilight in "Princess Twilight Sparkle". Twilight even mentions it and suggests Rainbow Dash take over to teach Spike the most advanced techniques. Spike also crashes into the ground, leaving a trench in his wake, just as Twilight did
- Sludge's overall goal — kicking Spike out of his own home and taking everything from him — parallels the story of how Scales stole everything from the previous Dragon Lord. Although he doesn't mention directly the story, Sludge affirms that it is "what dragons do".
- Sludge is surprised that the Mane Six have been to Klugetown. Mount Aris and the Storm King's defeat are also referenced.
- Calling Parents by Their Name: Spike twice acknowledges that Twilight reared him and implies he sees her as his parent, yet he always calls her by her name.
- The Cameo:
- Big Macintosh and two of the Wonderbolts appear while the Mane Six help Sludge recover.
- Dragon Lord Torch shows up in Sludge's fake flashback.
- Starlight Glimmer appears briefly in a painting of herself and Twilight hanging in a corridor, and later when Sludge interrupts her bath by throwing her out a window, tub and all.
- Con Artist: Sludge turns out to be one, lying about being Spike's dad so that he could live in the lap of luxury in Twilight's castle.
- Continuity Nod:
- Cool Big Sis: Smolder seems to become this toward Spike in scenes such as teaching him how to fly, as well as being supportive toward him and protective of him when Sludge turns out to be exploiting Spike all along.
- Daddy Had a Good Reason for Abandoning You: When Spike asks why he was orphaned, Sludge finds himself spinning a long-winded tale explaining this. According to his story, he was absent because he was imprisoned by "scale collectors".
- Destination Defenestration: During "You Just Can't Be a Dragon Here" Sludge starts throwing things out the window, including Starlight Glimmer taking a bath.
- Disappeared Dad: Sludge claims he is Spike's long lost father.
- Does This Remind You of Anything?: Sludge being in nothing but a bathrobe and making Twilight visibly uncomfortable is reminiscent of those who sleep in the nude.
- Everyone Has Standards: Smolder doesn't take it well when she finds out how Sludge has been treating Spike.Smolder: Dragons are rude and rebellious, but they aren't lazy lumps who take advantage of their kids.
- Fade Around the Eyes: Sludge's Villain Song concludes with the light dimming until only his eyes stay visible. Then we go to a commercial break.
- Fan Disservice: Seeing Sludge in a bathrobe isn't a pretty sight, to say the least.
- The Farmer and the Viper: The Mane Six and Spike take Sludge in to help him recover and heal. He repays them by lying to Spike about being his father, moving into the castle and having Spike wait claw and tail on him.
- Fat Bastard: Sludge is the fattest dragon yet seen, and he's definitely not a nice guy.
- The montage of the ponies helping Sludge to recover gives us hints of how greedy and lazy he really is.
- The holes that the Mane Six and Spike point out in Sludge's story of how he "lost" his son, such as knowing Spike was a boy before he hatched and how the egg ended up in Equestria, are a major clue that he is lying about being related to Spike.
- Also, his wonderment at the ponies being at Kludgetown hints that he used that knowledge to tailor a made-up location the ponies have never been and thus be unable to confirm.
- When Spike asks if there are any father/son activities Sludge always wanted to do, Sludge replies, "Not really," before catching himself.
- Smolder cutting in to take over Spike's flying lesson from Twilight reaffirms that, having grown up in the Dragon Lands, she knows enough about how dragons work to step in as a Big Sister Mentor to Spike. This comes up again later when she actually hears some of the things Sludge has been telling Spike about dragons.
- Forgot About His Powers:
- When Spike crashes during his flying lesson, Twilight doesn't bother using her levitation magic to stop him.
- When Spike is celebrating the fake Hearthswarming Eve, Rainbow sprinkles flour outside the window to mimic snow. Pegasus ponies have weather-manipulation magic and can thus create real snow on a whim.
- Gasp!: Sludge telling Spike he is his father elicits a collective gasp from the ponies — with Pinkie's lasting a lot longer than the others.
- Gross-Up Close-Up: During Sludge's song, on the verse where he complains that dragon don't brush their teeth, we get a close-up of his jagged, very gross teeth blackened in spots.
- Happily Adopted: Spike is not bothered by the lack of information about his biological Mother and later dismisses Twilight's offer to look for his biological family, because he considers her to be his real family.
- Hate Sink: Sludge gets a young dragon's hopes up that he's his long lost father, only to exploit him, belittling the fact Spike wasn't reared by dragons, and alienate him from his friends just so he could essentially be Sludge's servant. He was intentionally designed to be unlikable.
- Heroic Sacrifice: Sludge claims he pulled this. The Scale Collectors told him he could either hand Spike's egg over, or be their prisoner. According to his story, he chose the latter.
- Hold Your Hippogriffs: Apparently, dragons use "waiting claw and tail" in place of "waiting hand and foot."
- Hypocrite: Sludge teaches Spike how all the luxuries of the castle are preventing Spike from being a "real dragon" while pretending to be his dad, but he has Spike bring him all his luxuries and snacks so he can enjoy them himself while he tells Spike to sleep outside like a "real dragon." When the truth is revealed, he departs, spitefully telling Spike to "enjoy lovin' pony town," which was exactly his plan.
- Ironic Echo: When Spike and Smolder convince Sludge that Twilight no longer wants dragons in the castle, the young dragon sings a short reprise of "You Just Can't Be a Dragon Here".Spike: [singing] This bed is much too soft, just take that silk robe off, we can't be dragons living here.
- Karma Houdini: Sludge never gets any comeuppance for lying and exploiting Spike; he even keeps the pillow he steals from Spike — though he is forced to abandon his newfound life of luxury and fend for himself in the wild again.
- Lazy Bum: Sludge, down to a T. Smolder even calls him this when she hears how he is treating Spike.
- Long List: Spike had been working on one full of activities he could do with his dragon parents. Said list unfurls and rolls several feet away.
- Luke, I Am Your Father: Sludge invoking this starts the plot rolling.
- Missing Mom: In universe. Sludge's story claims that Spike's mother left on a life-time quest to chart a migration route.
- Motivation on a Stick: Pinkie exploits this trope to get Sludge up and moving as he's being rehabilitated, first with a cupcake on a stick with her on his back (to Twilight's shock), then by walking past his room with a cart full of gem-topped cupcakes that Sludge chases after.
- My Species Doth Protest Too Much: Before this episode, all dragons reared in the Dragon Lands (even the friendlier ones, like Ember and Smolder) were shown to be tough, independent, and self-sufficient. In contrast, Sludge is a fat Lazy Bum who prefers to lie around all day, being waited on by others.
- Naked People Are Funny: Played With. Ponies and dragons don't normally wear anything, yet it's still amusing to watch Twilight react to Sludge's nudity with abhorrence.
- Never My Fault: When Spike sadly lampshades the cruelty in Sludge's trickery, Sludge crossly responds, "Hey, don't give me that."
- Noodle Incident: One has to wonder what really brought Sludge to Ponyville in a fiery crater.
- Pastiche: Sludge's song is both musically and thematically similar to King Louie's "I Wanna Be Like You" from The Jungle Book.
- Pet the Dog: Downplayed. Sludge decides to do every item on Spike's Father-Son activity list to make the latter happy, though it might be mitigated by Sludge's ulterior motive to keep up the caring father act.
- Rage Quit: After Smolder twice shuts down his claims that he just did what any other dragon would do, he angrily says "I don't need this", and decides to leave rather than argue the point further.
- Recycled Soundtrack: The musical cue played during Spike's flying lesson in the opening scene is the same tune played during Twilight's flying lesson at the beginning of "Princess Twilight Sparkle - Part 1".
- Red Eyes, Take Warning: The "Scale Collectors" are depicted as shadowy creatures with glowing red eyes.
- Reveal Shot: A shot of the castle's window shows it is snowing outside, while inside Sludge and Spike exchange Hearth Warming's presents. A wider shot then reveals that Rainbow Dash is simulating the snow and that it's still summer outside, avoiding a too big Time Skip in-episode.
- Sadistic Choice: In-Universe, Sludge's story has one. When faced with the "Scale Collectors", they offered he either give up Spike's egg or surrender himself.
- Sludge's story involves an unknown country that is a World in the Sky populated by Dragon Hunters.
- The way Sludge reclines in Spike's bed simply screams "Draw me, Twilight. Draw me like one of your French ponies."
- Shorter Means Smarter: Downplayed; Sludge is easily the shortest adult dragon seen in the series, and he was smart enough to quickly come up with a halfway-believable story about being forced to abandon Spike's egg.
- Shut Up, Hannibal!: Smolder to Sludge when he confesses that he isn't Spike's real father and explains his motives:Spike: So... you... pretended to be my dad?
Sludge: Now-now-now-now-now, don't look at me like that, kid. I did what any dragon would do.
Smolder: No. You didn't.
Sludge: Hey. I saw an opportunity, and I took it. That's what dragons do.
Smolder: No. It isn't.
- The Sociopath: Sludge cares about nobody but himself, and he doesn't show any remorse in lying to the orphaned Spike that he's his father and exploiting him as a servant while he lives in luxury in the castle. One example is when he throws a bathtub out the window with Starlight in it, especially when he didn't know beforehand Starlight could catch herself.
- Technicolor Fire: Like many other dragons, Sludge's fire comes in a specific color — in his case, hot magenta with a yellow core.
- Uncanny Family Resemblance: Subverted in that Sludge isn't actually Spike's father, but he's similar enough in build, from the spikes down his head to his tail ending in a point, that one could be easily fooled.
- Ungrateful Bastard: Spike and his friends help Sludge recover after he crashes in Ponyville, and Sludge thanks them by lying about being Spike's father as soon as he learns that Spike was reared by ponies and proceeds to mooch off of Spike's hospitality.
- Unreliable Expositor: In Sludge's story, he paints himself as a loving husband and father who flew thousands of miles to reunite with his wife, and even gives himself a Heroic Sacrifice. Given what we know about Sludge later, it's all painfully inaccurate.
- The Unreveal: Given Sludge's story about "coming" to Ponyville wasn't true, we're still left to wonder how Spike's egg ended up at Celestia's school.
- Villain Song: Sludge gets one, "You Just Can't Be a Dragon Here".
- Watch Out for That Tree!: During Spike's flying montage, he turns his head and waves at Twilight, right before flying smack into a tree.