Phineas, Ferb and their friends set off to find the lost city of Atlantis, while Candace enters a sandcastle contest where Jeremy is judging. Meanwhile, Doofenshmirtz decides to create an evil plant growth formula to turn all the plants in the Tri-State Area into thorny, prickly minions.
Tropes:
- All for Nothing: After discovering Atlantis, Phineas, Ferb, and their friends decide to bring it up to the surface for the whole world to see, using weather balloons and helium canisters. Unfortunately, they executed this plan around the same time Perry attacks Doofenshmirtz's genetically-modified plants with weed whackers. Upon being thrown out of the blimp window, the thorny plant parts pop the balloons, causing Atlantis to sink back into the ocean floor. The kids were disappointed that no one saw Atlantis (not counting Jeremy due to him assuming that it was Candace's sandcastle), with Ferb deducing that it wanted to stay lost forever. Irving comments while taking pictures from his mind that he forgot to take off his thumb from the "lens" and all he remembered now was his thumb.
- Artistic License – Geography: The gang pass by the remains of the Titanic, which are supposed to be off the coast of Newfoundland, and Amelia Earhart's plane, which is supposedly somewhere in the Pacific Ocean, both of which are long ways away from the mainland United States.
- Atlantis: The episode has the boys discover the titular lost city.
- Beach Episode: Mainly on Candace and Linda's end.
- The Burlesque of Venus: At one point, Baljeet does the "Birth of Venus" pose inside of a giant clam.Baljeet: And everything is so pretty.
- Camera Obscurer: After Irving's camera is stolen by an eel, he relies on taking imaginary photos instead, but in the end, he finds out he left his thumb in front of the "lens" the whole time.
- Copycat Mockery: Agent P receives his mission from Carl who does an imitation of Monogram.Major Monogram: Are those my old mustache clippings?
- Cutting the Knot: When Phineas spots the door to the City of Atlantis, he points out that it has instructions written in ancient text on how to open it. Buford decides to ignore the text and punches his fist into the door, which actually works.
- Failed a Spot Check: Candace doesn't see Atlantis behind her, nor does Linda. Jeremy does, and he tells Candace she won the sandcastle contest. Candace assumes that Jeremy was referring to the half-collapsed castle because of this, and as she and Linda talk, Atlantis sinks, and they both miss it completely.
- Gone Horribly Right: The evil plants Doofenshmirtz raised to do his bidding are so big and violent that they grow all over Doofenshmirtz's blimp and tie him up.
- Hurricane of Puns: Doofenshmirtz constantly teases Perry with plant-based puns as he explains his evil plan, laughing at his own jokes as he does so.Doofenshmirtz: Your efforts to try to stop me have been fruitless. Fruitless. Y-you like that one? Yeah, that's a good one! Fruitless? Next time you'll "leaf" me alone! Heh heh heh. Yes, Perry the Platypus, I can be a fun guy. Get it? Fungi? The plural of fungus? Heheh... it's a... Yeah.
- Inconsistent Episode Lengths: This episode clocks in at around nine minutes, which is the shortest episode segment of the show. This was due to the length of its sister episode, which comes in at 15 minutes.
- Instantly Proven Wrong: Candace says she went to the beach for peace and quiet, but is immediately interrupted by Phineas and the gang shouting and having fun.Candace: I spoke too soon.
- No Ending: On Candace's end, as she and Mom leave to get the blue ribbon and fail to notice Atlantis.
- Paste Eater: Baljeet exclaims that Buford drank all his sunscreen. Buford says that the coconut flavor is his favorite.
- Patter Song: The Atlantis song.
- Plot Allergy: Doofenshmirtz turns out to have an allergic reaction to the plants he's raised.Doofenshmirtz: Curse you, inadequate immune system!
- Putting the Pee in Pool: Implied. As the gang walks under the sea in search of Atlantis, Baljeet complains that the water feels warm when standing next to Buford.
- Save the Villain: Perry leaves the blimp but later comes back with a hedge trimmer and a circular saw to cut the evil plants and free Doofenshmirtz.
- Seahorse Steed: Isabella mentions that she hopes to see a seahorse so she can get her Underwater Equestrian Patch. A few scenes later, when they see a group of seahorses and Baljeet tells her she can get the patch, Isabella says, "That was a joke. They're way too small to ride." Buford then proves her wrong by scooping up a bunch of them and riding all of them at once.
- Shout-Out: Candace says she used to be good at building sandcastles, but now she's "Frank Lloyd Wrong
". - Street Musician: A street musician sings Agent P's theme song as Perry uses his guitar case to make his entrance into O.W.C.A. headquarters.
- Tempting Fate: Candace in the beginning of the episode, when she says "Nothing but the waves, the sun, and a little peace and quiet":Baljeet: Buford drank all the sunscreen!
Buford: Coconut's my favorite flavor!
Isabella: Who wants to play volleyball?
Candace: I spoke too soon.
