When a giant cake (actually a cake shell) has a person (usually a bachelor party stripper) hidden inside, so he or she can jump out of it for dramatic effect.
Girls have been jumping out of cakes since Evelyn Nesbit did it for millionaire playboy Stanford White in the Gay Nineties, but the practice of enclosing a living creature inside a cake or pie shell goes back to medieval days. It's the origin of the nursery rhyme "Sing a song of sixpence", where live blackbirds are put in a pie shell for a king's feast.
Mostly Played for Laughs, especially if the cake is at an unexpected (and inappropriate) place (like a child's birthday party) or the stripper inside is replaced with someone else (a cop, an Abhorrent Admirer who crashed the party to get her object of desire, an angry fiancee or wife who suspects that her husband will have too good of a time at his buddy's bachelor party, a Dirty Old Woman who used to be an adult entertainer when she was young and is still entertaining in her autumn years, a cross-dressing Camp Gay man who decided to come out of the cake—and the closet—all in one night, or a heterosexual man who was put in drag and put in the cake as a cruel joke).
Sometimes played for drama (or really dark comedy) if the man of the hour is Too Dumb to Live and thinks the novelty cake is a real one (and cuts it, either injuring or killing the girl inside), if a Mafia hitman is inside the cake and shoots everyone at the party (though it can be softened up to being funny if the hitman is dressed in outrageous and obvious drag), or if the stripper dies of suffocation inside the cake and no one realizes this until it's too late.
- There was a phone commercial on how an old guy ended up delivering a girl-in-cake to a kid's birthday party. The point of the commercial was that it could have been prevented if his bosses could reach him, but he has no phone.
- At the end of Dragon Half (the manga), Rufa bursts out of Mink and Dick's wedding cake to announce the appearance of another Demon Lord.
- In "Dalton City", a Lucky Luke story, a saloon dancer is concealed inside a giant cake, but the homemade pastry is so tough that, by the time she manages to get out of it, the party, the fight and pretty much the story are over.
- In the Batman comic, one mob boss was killed by The Tallyman this way.
- In Secret Six, the rest of the Six hire a stripper dressed as Scandal Savage's dead girlfriend Knockout to hide in a cake and give her a lapdance on her birthday to cheer her up, but Scandal is too drunk to really realize what's going on (plus Knockout seems to possess the stripper for a moment to tell her to be happy). However, later Scandal meets Liana (the stripper) in a supermarket and they start dating.
- One wordless Mad Magazine strip had a gang boss hearing the noise of someone within his cake and machine-gunning it, visualizing a gunman hiding within a la Some Like It Hot. The second panel shows him blushing as they carry the stripper off in a stretcher.
- A Don Martin comic had a lab-coated scientist who built an automatic cake machine. Its robot arms pick up the various ingredients (milk, eggs, flour)-- then grab the scientist. After the finished cake emerges from the machine, the confused scientist jumps out (or is bounced out) in stripper wear.
- One of the final issues of Excalibur has a supervillain hiding inside of the cake at a bachelor party (after replacing the stripper inside and leaving her bound and gagged in a closet) so he can assassinate the unsuspecting partygoers.
- Scrooge McDuck once went to visit one of his hotels when the manager mentioned a convention. Unfortunately, it was a Convention of Crime organized by the Beagle Boys and other criminals. They ordered a cake and Scrooge was told someone would come out of it. Scrooge ordered whoever was in the cake to show up and he found Madam Mim. When she asked about the outlaws she was supposed to present herself to, Scrooge told her they were all arrested. Since she had already been paid, she left without caring. Scrooge and the hotel manager then got cop costumes and jumped out of the cake, scaring the bad guys.
- One Little Annie Fanny comic in Playboy had someone hire Annie to do this for someone's surprise birthday party (she was told). In a twist on the theme, it was her surprise party.
- In the Harry Potter/Sailor Moon/Ranma ½ crossover fic The Girl Who Loved, the idea is discussed by Usagi in the context of Harry's bachelor party, and separately by others as well. Luna Lovegood, Makoto, Minako and Hermione (!) all volunteer or consider being the girl in the cake. We don't actually see the party, but evidence later in the story strongly suggests Hermione actually did it.
- A gunman hidden in a cake is a pivotal part of the plot at the climax of Some Like It Hot.
- Erika Eleniak jumps out of a cake at the beginning of Under Siege and promptly gets dragged into Die Hard on a battleship.
- Kathy Seldon in Singin' in the Rain comes out of a cake at a Hollywood party. This after she gave Don a lot of grief about how she was a stage actress, as opposed to doing "just a lot of dumb shows" on films.
- In How To Murder Your Wife, avowed bachelor Stanley Ford meets the future Mrs. Ford this way. She later says it was the only job she could get after someone stole all her clothes.
- Gruesome example, courtesy of the Addams Family movie: Gomez arranges for a stripper in a cake for Uncle Fester's birthday. Unfortunately...
Gomez: Lurch...was she in there before you baked it?
- In the Discworld novel Night Watch, "Homicidal" Lord Winder has his guards stab the giant cake at a party to check for assassins inside (several times at different levels, in case it's a dwarf or someone kneeling down). He does get assassinated later at that same party, but it has nothing to do with cake.
- One of these factors into a Zany Scheme hatched by GOB in Arrested Development.
- Boardwalk Empire has Nucky's girlfriend do this for his birthday.
- In one episode of Cheers, waitress Diane Chambers is hidden inside a cake when Sam Malone says something offensive about her. She pops out of the cake (dressed in a Stripperific costume) and is angry at him.
- Woody, who was assigned the job of getting the stripper, had asked Diane to be the stripper who pops out of the cake at Sam's bachelor party, when Sam and Diane were getting married. Woody didn't get that the stripper was supposed to be someone other than the bride-to-be. Diane agreed to it because she was offended that Sam would even have a bachelor party with a stripper.
- Hetty from NCIS: Los Angeles once hid in a cake, but it's unclear why.
- The Mads' Invention Exchange for the I Accuse My Parents episode of Mystery Science Theater 3000 was "Cake & Shake", a cake mix with a real exotic dancer included.
- In the opening scene of the Doctor Who episode "The Vampires of Venice", the Eleventh Doctor jumps out of a cake at Rory's bachelor party.
The Doctor: Rory! That's a relief. Thought I'd burst out of the wrong cake... again... That reminds me, there's a girl standing outside in a bikini. Could someone let her in and give her a jumper? Lucy. Lovely girl. Diabetic.
- According to the stories, Bill Brasky got one of these at his bachelor party. Before anyone could tell him about the girl, he'd already eaten the entire cake...
- In the Married... with Children episode "Peggy Loves Al, Yeah, Yeah, Yeah", Marcy plans to do this for Steve as a Valentine's Day present. Al has the cake delivered to the locker room of the Chicago Bulls.
- In the Xena: Warrior Princess episode "Soul Possession", Joxer organizes a girl jumping out of a cake for Ares' bachelor party. It turned out to be Meg, an Identical Stranger of Xena, who he was going to marry.
- Referenced in a Twisted Cakes episode of Food Network Cake Challenge, where the cake was made to look as though it and a stripper inside had had a large slice taken out of them.
- There's an episode of My Family where Susan is unhappy about Ben planning to order a cake with stripper for the bachelor party he's hosting. She decides to take the stripper's place inside the cake, only for the cakes to be mixed up. Hilarity Ensues.
- On The Drew Carey Show, Drew's brother Steve thought Drew's bachelor was the perfect place to jump out of a cake, in full drag, and explain to their father that he was a transvestite.
- The Nanny: Fran Fine wasn't worried about her soon-to-be husband attending a bachelor party until her mother stating she once knew a man who left his bride for the woman who came out of the cake at his bachelor party. The man was Fran's father. She then entered the cake of Max's party and came out of it, right after Max's brother told him about his relationship with her. Fran then got back inside the cake.
- Newlyweds Nick and Jessica: Nick's birthday. Guess who's hiding in that cake.
- In one of the Spider-Man stories on The Electric Company, the villain is the Birthday Bandit, a crook who crashes birthday parties in order to rob them. Naturally, the Friend to All Children hero is on his trail, and at his next heist, the Bandit finds no guests and a very big cake. He's not stupid and suspects Spidey is hiding inside waiting to ambush him, so he grabs a big club and crushes it - no such luck, as Spidey is actually hiding in the equally-large gift box, and while the villain is preoccupied with the cake, apprehends him with his webbing.
- Bob Martin sees one at the American Legion party in "Third War Rag":
Birthday cake about ten feet tall,
- In a Garfield strip, a female mouse jumps out of a cupcake, as a present for Garfield's birthday. He remarks: "I'm not eating that."
- Inverted in Close to Home, much to the confusion and near-panic of the people in the cake. The model, meanwhile, looked quite satisfied.
- An inversion can be seen in an original cartoon by Charles Addams: an all-male birthday party cheers as the giant cake is wheeled out—and then all look disappointed at their giant slices of cake. (Except for the birthday boy himself, oddly enough.)
- Jim Gaffigan mentions this trope in his Beyond the Pale special, and how nobody ever does it with pie. "'I'm here!' 'Go take a shower.'"
- In New Super Mario Bros. Wii, the Koopalings hide in a cake to kidnap Peach.
- In The Sims you can buy a giant cake to have a dancer come out and dance. Of course you have to keep children out of the room. The dancer can be of either gender (and you can hire both with two cakes) Rarely a gag dancer, like a person in a monkey suit, will come out instead.
- The Perry Bible Fellowship strip "Miggs".
- At the end of this Hark! A Vagrant strip.
- The Whiteboard used this for the second anniversary.
- In a certain Kevin and Kell strip, "Pop Goes the Weasel" was being played during a birthday party for Coney. When the song ended, an actual weasel popped out of the cake and Coney ate it.
- Barking Crayon has a case of confusion over how this works.
- Girl Genius has the moment when Doctor Dio Zardeliv discovered the downside of his new popularity.
- Nerf NOW!! in (belated) 10th anniversary strip.
- In Red vs. Blue, apparently Donut did this for Sarge's birthday while wearing his 'Officer Hotpants' uniform.
Simmons: Oh my God, that cake is huge! It's big enough to fit a person in it.
- Family Guy had one with a stripper. Peter accidentally kills her while cutting the cake but is concerned only that the cake has coconut frosting.
- The Flintstones episode "Frantic City": The cake at the Water Buffalos' convention was supposed to have showgirls inside. It had their angry wives instead, rolling pins in hand.
- The Simpsons episode "Rosebud"  had a part where Smithers imagines his boss, clad in only a sash popping out of a cake after Mr. Burns grumbles that he's not going to get what he truly wants for his birthday (with Smithers adding that no one ever does).
- Another episode of The Simpsons had the residents of the old folks' home try to cheer up Grampa with a stripper in a cake, but she died while they were wheeling the cake to him.
- Another episode parodies this with McBain jumping out of an ice sculpture and gunning down everyone in the room. "Ice to see you."
- The South Park episode "Butters' Bottom Bitch" has an undercover cop posing as a hooker in one of these.
- In the intro to The Critic (the FOX version, not the ABC version), when Jay's family presents him a birthday cake, his Cloudcuckoolander father wearing a "Happy New Year 1937" sash jumps out.
- In "The Unmentionables" (1963), Bugs Bunny (in flapper drag) does the pop-out-of-a-cake bit at a birthday party for the head mobster.
- In "Blooper Bunny", Yosemite Sam pops out of the cake during Bugs Bunny's anniversary celebration. Behind-the-scenes footage shows that he's adamant about it.
Do I look like some hootchie-cootchie girl to come a-shimmin' out of a cake? Why, it ain't decent!
- The debut of Harley Quinn in Batman: The Animated Series had her doing this to capture some police officers, and in fact Harley was created because it was thought that The Joker doing this would be too bizarre.
- Paul Dini says this, but in the actual episode, Harley pushes the cake in, and the Joker DOES jump out of the cake.
- In the Word Girl episode "Becky's Birthday" an energetic Bob the monkey does this.
- In Futurama, the crew is holding a birthday party for Nibbler. Leela tells Bender to make a cake. She adds that if he plans to have a stripper jump out of it, he needs to bake the cake first.
- Kim Possible: In "The Big Job", Junior begins to explain that he sprung Shego from prison because his father's birthday is coming up. Shego cuts him off with "I don't do cakes, okay? I don't bake 'em, and I don't jump out of 'em!" The writers were surprised the line passed censors.
- God, the Devil and Bob: When the Devil removes evil from the world due to God forgetting his birthday, Bob is horrified to discover that bachelor party cakes now contain eldery couples who give advice on married life.
- Reportedly, Czar Peter the Great of Russia amused his friends by hiding a naked woman in a cake at a party. Hardly out of character for that hard-partying monarch.
- Ivan the Terrible never did. Make of that what you will.
- Old joke. The woman gets in the cake before it is baked....
- Inverted in this tasteless joke: "What's the difference between a normal bachelor party and a bachelor party for a bulimic? At a bulimic's bachelor party, the cake jumps out of the girl."
- The one where Mr. Burns finds his long-lost teddy bear