"X Marks the Ed" is the 11th episode of Season 3 and the 63rd episode of Ed, Edd n Eddy. In this episode, Eddy gets a huge pimple and is aided by Rolf, who tries to help make it disappear while at the same time trying to not let others see it.
The Eds, looking for some easy money, decide to catch some fish from Ed's backyard pool to sell, only to find themselves with absolutely no success. Despite Edd's skepticism that they'll actually find anything, Ed claims he got a bite and, upon pulling his Fishing Pole, the Eds find a fish-like creature constructed from various foodstuffs (Ed's Freezer Experiment, which Ed reveals that Sarah had hidden after he cleaned it out of their freezer) at the end of the fishing rod. Ed, clearly happy to see it again, thrashes it back into the water, causing a wave that sends them flying into a bush. Eddy, after recoiling, immediately pounces on Ed to reprimand him about ruining scams, but Ed seems to be distracted by something else. After being asked by Eddy as to what he's looking at, Ed takes Eddy to the pond to see his reflection, revealing a red lump on top of his head. Upon an observation by Edd, Edd reveals it's nothing more than a pimple and that he should be proud of it, as he's now reaching adulthood. However, Eddy, embarrassed, wishes to hide it. Ed tries to help Eddy by rubbing it off (without any success). Edd tells Eddy to stop worrying; however, Eddy decides to hide when Ed calls for Jonny and Plank. Despite hiding the bush, Ed finds Eddy and showcases it to Jonny. Eddy, after facing some rather insulting jokes, suddenly disappears.
Eddy, desperate to conceal his problem, tries to use his dad's wig to conceal his problem, only for it to be attacked by Ed. Edd then tries to help Eddy by trying to conceal the "zit" with some foundation, only for the pimple to grow bigger. Eddy turns back to tell Edd he'd made it bigger only to find that Jonny had been charging the kids 25 cents to see his zit. After a round of humiliation (which made his pimple grow considerably) by The Kids and Ed, Edd angrily tells them to leave the house, disgusted by their antics over Eddy's pimple. Ed then sadly leaves, but Edd tells him that he doesn't have to leave, which causes him to happily come back. Rolf, sympathizing for poor Eddy, tells The Eds to stop by Rolf's House in 1 hour to get rid of the zit. Eddy, albeit frightened, agrees.
The Eds try to get Eddy across the street to Rolf's house, unnoticed, but the Kids suddenly appear and begin to take photos of Eddy's pimples, and are chased to Rolf's House. Luckily for The Eds, Rolf manages to drive them away. Rolf begins making Carbuncle of the Flesh Stew, a remedy he'd learned about in The Old Country that is handed down through many pimply-faced elders. He gets Eddy to marinate in a barrel full of lard and Edd and Ed to help him prepare the broth, which includes softening a squid and grating a turnip. Rolf then adds the Pickled Towel of Mith and states that the simmering of the towel takes 14 days and 14 nights to prepare, which shocks Eddy. Rolf then exclaims that he'd thought ahead and pre-made one in advance. He then takes a towel out of the broth and places it on Eddy's head. After a few seconds, he then kicks Eddy out of his back door. Rolf then places a crate on his head and then places a chicken in the crate, claiming they must be quick. The said chicken then starts pecking down on the pimple continuously. Ed states to Edd he really wants a chicken peck on the head, but Rolf tells Ed and Eddy to pick Eddy up in 24 hours, which Rolf spends carving a wooden shoe.
After 24 hours, Ed and Edd return to pick Eddy up. Rolf pulls Eddy out of a Giant Tomato and shows Eddy his face, revealing that his pimple is gone, but his head has been shrunk considerably and he had a higher pitch voice. Eddy, outraged, demands for Rolf to fix his head while Edd, intrigued, asks for an explanation as to how he did it, while Ed asks Rolf to shrink his head, too. The episode ends with the Eds chasing Rolf around his backyard to get him to shrink Ed's head, to fix Eddy's and to provide Edd with an explanation.
When the Eds were "fishing," Eddy wasn't wearing shoes. After the Eds are flung out of the pond, Eddy is wearing shoes, even though he was not seen putting them on.
Eddy's reflection in the pond does not show his shirt stripe on the opposite side. Rather, it is still to his right.
Ed applies a toilet plunger to Eddy's bib-covered head. When Eddy's reflection is shown in the bathroom mirror, the bib has vanished, but the toilet plunger remains.
Nazz's mouth does not move when she says "What's happening, guys?"
When Sarah yells "Over here, weirdo!" the captioning mistakes her for Jonny.