It's a big day for the Cakes: they're entering their newest cake recipe, the "Marzipan Mascarpone Meringue Madness" (or MMMM), in Equestria's National Dessert Competition, and Pinkie Pie is going to make sure that the cake gets there in one piece... even if she has to shanghai Big MacIntosh and the rest of the Mane Six into getting it aboard the Friendship Express.Once aboard, the gang meet some of the other competitors: Gustave Le Grand, a snooty French griffon who thinks his "Exceptionally Exquisite Eclairs" are a shoo-in for first prize; Canterlot's own Doughnut Joe, who's looking to make his doughnut shop world-famous with a scale-model city made out of pastry which he calls "Doughnutopia"; and Mulia Mild, who thinks she deserves the top prize with her intricately sculpted Chocolate Mousse Moose. Rivalries flare, but Twilight manages to calm everypony down and convince them to get to bed early... except Pinkie Pie, who insists on standing watch out of fear that one of the other chefs will sabotage the MMMM.As the night drags on and Pinkie nearly nods off, she's jolted awake by shadowy figures darting through the cars. She chases them from one end of the train to the other, but somehow loses them both. Pinkie returns to the dessert car to check on the Cakes' cake when the curtains descend, leaving Pinkie Pie in the dark. Once the curtains are re-opened, Pinkie resumes her vigil convinced that her paranoia was justified... only to immediately nod off.Morning comes, and Pinkie awakens to find the MMMM intact... or not, as Twilight Sparkle points out. Pinkie resolves to find out whodunnit by dressing up in a deerstalker cap and bubble pipe and dragooning Twilight Sparkle into playing Watson to her Sherlock Holmes. Pinkie Pie wastes no time in accusing each of the other bakers of being the guilty party, complete with ludicrous flashbacks to how they did it:
She first accuses Gustave Le Grand, in the style of a silent movie, of tying Pinkie to the railroad tracks and chopping up the cake with a saw blade. Twilight is quick to point out that Pinkie is clearly not tied to the train tracks and that the cake was bitten, not sliced.
Next, Pinkie accuses Joe... or rather, notorious super-spy "Con Mane", who knocked out Pinkie Pie and destroyed the cake with an arsenal of spy gadgets. Twilight shoots this theory down, too, citing the lack of a laser beam security system and Joe's non-spy physique.
Pinkie decides that must mean Mulia Mild is the culprit behind the destruction of the cake, and a ninja for some reason. Twilight points out the brow-beaten Mulia is probably not a secret master of the martial arts.
Pinkie Pie is forced to conclude that there's no evidence the other bakers were behind the sabotage of the MMMM and not only that, but she starts to wonder why the other desserts, as tempting and delicious as they look, were completely untouched. Then the train passes through a tunnel, plunging the room into darkness again... and upon the train leaving the tunnel, all the desserts are in ruins and Detective Pinkie is completely stumped.
Pinkie Pie: Now I have no idea who-do-dunned it!
Twilight takes charge of the investigation and sends everyone back to their rooms while she and Pinkie Pie look for clues. The first order of business is to retrace Pinkie Pie's steps from when she was chasing the shadowy figures the other night. Through her thorough investigation, Twilight finds enough clues to figure out the culprit and tells Pinkie Pie to gather everypony together.Once the other passengers are assembled, Twilight reveals her clues one by one. The first is a blue feather left behind in the caboose. The second is a lock of pink hair found in the conductor's hat. The third and final clue is a false eyelash stuck to the portrait! This means that Pinkie's friends Rainbow Dash, Fluttershy, and Rarity were all responsible for taking bites out of the Marzipan Mascarpone Meringue Madness! The two pegasi and the false-eyelash-wearing unicorn ask for forgiveness, which Pinkie cannot refuse.That still leaves the question of who ate the other bakers' desserts... a question that Pinkie Pie is eager to answer, now that she knows to look for clues. Mousse in Gustave's mustache, eclair in Doughnut Joe's hair, and sprinkles in Mulia's wrinkles reveals the truth — they each devoured each other's entries! The bakers confess to being unable to resist eating each other's desserts after Pinkie Pie's vivid descriptions. The mystery has been solved but now no one has an entry for the contest... or do they?At the competition, we witness Pinkie narrating a letter to Celestia about not jumping to conclusions...before a massive cake made from the remnants of the damaged desserts is revealed to the the judges. It instantly wins the blue ribbon and after wrapping up her letter, Pinkie Pie promptly consumes the whole dessert in one gulp! As everyone joins in laughing with thesuper stuffed and chubby cheeked Pinkie Pie, the episode ends with the fourth wall being promptly 'eaten'.
Tropes present in this episode (YMMV tropes can be found here):
Pinkie scratches herself like a dog when she wakes up the next morning. This is something some ponies and foals can do, though full-grown, normal-sized horses are incapable of it. She also growls like a dog while pursuing the thief.
Applejack pants and drools while Pinkie is describing the MMMM. Pavlov would be proud.
All Your Powers Combined: The confection at the end is the Cake's cake, decorated/repaired with Gustav's eclairs, Joe's donuts, and the head of Mulia's chocolate moose. The judges clap eyes on it and award it 1st prize then and there.
Balloon Belly: Pinkie Pie gets a very noticeable one (with accompanying chubby cheeks and double chin) at the very end of this episode, after devouring the huge cake in one bite.
Behind the Black: There are several times where Pinkie is at the same angle Twilight was at when she saw the damage to the cake, and yet she didn't notice it until it was in frame; a downside of Pinkie's Fourth-Wall-Breaking abilities?
Big Eater: It's easy to miss that, in a Pinkie Pie episode, the three chefs reduced the baked goodies to leftovers in the less-than-a-minute the train spent in that tunnel!
And Pinkie Pie forever cements her Big Eater credentials by devouring a cake bigger than her entire body in one gulp by jumping into the air and diving down on it, mouth wide open, triggering her stomach's size to triple as well.
Bling of War: The compartment aboard the Friendship Express where the desserts were stored is decorated with a portrait of a pony wearing a Napoleonic-style uniform bedecked with brush epaulets, medals and a sash. For good measure, he also has a Badass Mustache.
In the past the Cakes have been hesitant to trust Pinkie to be responsible and were impressed when she proved herself. Now they are entrusting her with a big responsibility and she is determined not to disappoint them.
In The Best Night Ever, it's revealed Rarity wears fake eyelashes, which prove to be a clue to implicate her in eating Pinkie's cake.
In Read It And Weep, Pinky Pie reveals that she likes reading as much as the next pony. In this episode, Twilight Sparkle claims that she knows how to solve real-world mysteries due to having read mystery novels. Immediately after, Pinky starts thinking in terms of mystery tropes, revealing that she must have been reading mystery novels as well.
Carrying a Cake: How they get the "Marzipan Mascarpone Meringue Madness" to the train. Averted in that they manage to get it to the train safely (despite several near mishaps), if not to its ultimate destination. Pinkie made sure of that.
That painting of a mustached stallion looks pretty normal, doesn't it? Except he has long eyelashes.
Also notice how Rarity's right eye is never shown after the cake incident.
Though there are no post-cake-munching visual clues for the viewer, the two shadowy figures that Pinkie chases down from the exterior train shown are drawn with the distinctive features of Rainbow and Fluttershy, respectively.
All Pinkie's Imagine Spots all have the cake being sliced to pieces, even after Twilight outright tells her after the first one that the cake wasn't cut at all. Also everything else she "deducts" until she solves the second mystery, especially her interpretations of Twilight's evidence.
"Fine, I'm guilty! I wear false eyelashes! Oh, and I took a bite of the cake."
Among the suspects on the train are characters and species from previous episodes, including amule (Mulia Mild), a griffon (Gustave Le Grand), and Joe. And of course, the same Friendship Express Train and stations are used as the settings.
Pinkie's distinctive gasp from the pilot is recycled when she sees the damaged cake.
Back in "Griffon the Brush-off", Pinkie proclaimed that she was sure that other griffons would not be as mean as Gilda, even though she hadn't met any. First impressions aside, the griffon in this episode indeed turns out to be much more civilized.
Cosmetic Horror: Rarity considers her false eyelashes a dark secret, and pulls her mane over her lashless right eye in shame.
Crazy-Prepared: Pinkie's Holmes-ian hats could be attributed to Rule of Funny, but why did Twilight bring evidence bags with her to a dessert contest?
Dastardly Whiplash: Gustave is portrayed as this in Pinkie's imagination. They nail the trope down to the very. last. detail. In reality, he twirls his mustache during his hammy moments.
Easily Forgiven: Fluttershy, Rarity, and Dash ruin a cake that took the Cakes months of planning and hard work to make... and are forgiven the instant they say sorry.
Evil Laugh: Parodied with Donut Joe when he talks about his donut creation like he was about to take over the world, and with Gustave in Pinkie's Imagine Spot. The latter has to be spelled out in the intertitle, since it's a Silent Movie.
Evil Plan: Pinkie is positive that the other pastry producers have a fiendish plot to pulverize the MMMM while everypony is asleep so they can win the contest. This is why she stands guard.
Fun with Acronyms: The Marzipan Mascapone Meringue Madness cake is called the "MMMM" for short.
GASP!: Pinkie Pie when the damage to the cake is revealed.
Genre Savvy: Both Twilight and Pinkie exhibit this trope. Twilight claims to have read "many mystery novels," and therefore knows what to do, while Pinkie wastes no time crowning Twilight The Watson; going so far as to explain her role.
Hammerspace: Where Pinkie gets a bubble pipe and a pair of appropriate hats from.
Horrible Judge of Character: Pinkie's accusations towards the other bakers are particularly outlandish, as pointed out by Twilight. Even if Gustave Le Grand could be a moustache-twirling Silent Film Villain, Doughnut Joe is NOT an international Super-Spy, and Mulia Mild is an elderly donkey who is shaking and on the verge of tears at the end of Pinkie's accusation towards her.
Innocently Insensitive: Twilight clears Joe of suspicion by pointing out that he's not suave superspy material, but rather "big, gruff, and messy". Joe isn't thrilled by the description.
Joe:Hey!! Rarity:[conciliating] Although he would look rather dapper in a tuxedo. Joe:[says nothing, but looks remarkably flattered]
Insane Troll Logic: Pinkie's zany conclusions as to how each of the bakers destroyed the cake. They involve Milda being a ninja and Joe being a James Bond secret agent and both of them slicing a cake that has clearly been bitten.
No Peripheral Vision: Rainbow Dash escapes from Pinkie by flying close to the ceiling in the last train cabin.
No Sense of Personal Space: Pinkie - who else - literally climbs over every one of her suspects while looking for clues to who ate the other desserts.
Not so Above It All: Let's face it. No one expected Fluttershy to have taken a bite out of the cake. Also used in a deleted scene where Applejack would have also been guilty.
Pun: Pinkie pulls this trope multiple times. For example, "I have no idea who done dood it," and "Pegassistance".
Properly Paranoid: Pinkie expects that someone will try to eat the cake and later on wonders why no one went after the other bakers' pastries, but it's due to Pinkie's predictions and vivid descriptions that the pastries get eaten in the first place.
Red Herring: Early on, several of the other ponies are clearly enraptured by Pinkie's description of the MMMM, especially Applejack, who turns out to be one of the only ponies who isn't guilty of any cake-eating, and she's the first one who tried to take a piece off of it.
Rivals Team Up: In the end, Pinkie and all of the other chefs combine their creations and enter it as one dessert. It wins a blue ribbon.
Rhymes on a Dime: Pinkie with "Eclair in his hair" and "Sprinkles in her wrinkles"
Rule of Funny: Explains why Big Mac has trouble with a cake well within his weight class (though he might just be being excruciatingly careful rather than having difficulty with the weight) and why no one thinks of using a cart, or better yet, why Twilight didn't just carry the cake with her magic.
Schizo Tech: Pinkie's Imagine Spot for Joe turns him into a James Bond parody ("Con Mane"), complete with nifty spy-gadgets. Also, Twilight points out that there's no laser beam security system for the MMMM (as depicted in the aforementioned Imagine Spot), implying that lasers do exist, just not here.
We have a train, a mystery, and stolen food; Hmm...
Pinkie and Twilight don the appropriate hats and pipe for a full-on Sherlock Holmes take.
Each of Pinkie's Imagine Spots for the three chefs is a take on classic films: Gustave's as a Silent Movie; Pony Joe's as Con Mane, a parody of James Bond; and Mulia's as an old ninja film.
Pinkie Pie's Animesque Ninja Imagine Spot of Mulia Mild uses art style very similar to Samurai Jack's. Also, Ninja Mulia's jumping from train car to train car is very similar to that of Ryu Hayabusa from the NES series Ninja Gaiden.
Twilight's evidence bags are manila envelopes like the ones used in Clue. The tacked-on crimes and zany plot are also reminiscent of the film version.
Small Name, Big Ego: Pinkie in the role of the detective. Despite thinking that she is the best choice for the main investigator and Twilight (the smartest character on the show) should get the lowly, not-as-smart assistant job. Though she does redeem herself in the end with who ate the other three deserts, even after Twilight figures out who ate the MMMM by relegating Pinkie to the "lowly assistant" role.
Supreme Chef: The Cakes, Gustave Le Grand, Doughnut Joe, and Mulia Mild. Their irresistible creations don't make it to the competition whole, as various people can't resist pigging out on them, and the joint entry that they cobble together at the last minute easily wins the Blue Ribbon.
Toothy Griffin: Gustave Le Grand. Although only for expressiveness's sake, since bite marks on the cake are treated as a proof of his innocence, though the beak would figure far more prominently if he did take a bite out of it.
Traveling at the Speed of Plot: We know that the Friendship Express can get from Ponyville to Canterlot within a day, yet we have a full night cycle and hit one of the mountain tunnels at the most convenient time. It wouldn't be a good MMMystery without the night setting.
Unmoving Plaid: The plaid on Pinkie's deerstalker does not follow the corner of the hat.
With Friends Like These...: Three of Pinkie's best friends (Fluttershy, Rainbow Dash, and Rarity) ruin the cake. In a sequence that was cut out of the final script, Applejack admits to taking a bite as well; she only avoided being caught because she didn't leave any clues.