Sarah and Nazz are in a hallway of the school, applying lipstick, when a commotion comes from the gym. Inside, the Eds are working on a project that Eddy, of all people, actually likes. The point of the project is to establish a correlation between the nose's scent glands and the test subject's brain. Naturally, the test subject is Ed, who has a lid over his head, blocking out his eyes. Edd has brought a piece of pie in, and all Ed has to do is sniff his way towards it. Ed has nearly reached the pie when, much to Edd's surprise, he veers off. The reason Ed abandoned his course is simple: Eddy is holding up a rank-smelling gym bag and is using it to distract his friend. Edd reprimands Eddy, but Eddy ignores him, choosing instead to lead Ed into a wall once, twice, and finally three times. On this third attempt, Ed breaks through the wall and into the boys' locker room, where Jonny is offering an invitation to Kevin. Eddy takes no notice of this until Jonny hops up to them and offers them an invitation to his Arbor Day party as well before running off, presumably to invite everyone else. Eddy is ecstatic at having actually been given an invitation to a party, and he swiftly drags his friends away from the school so they can prepare for tonight, ignoring Double D's protests that they have to complete their project.
That night, the Eds head to Jonny's house. Ed and Edd are dressed in their best suits and Eddy is dressed to kill in his own semblance of party clothes. When they get there, Jonny eagerly invites them in, and Eddy does his best to make an entrance that will surely wow all the partygoers. When he bursts in, however, he finds that nobody is in the living room. Undeterred, he presumes that it's a kitchen party and slides into the kitchen. As in the first room he entered, there's no one there.
Well, perhaps not no one. Plank is sitting at a table in the corner, and according to Jonny some good jokes are being told. As only Jonny, Ed, and perhaps Plank himself can hear them, though, it's a pretty awkward situation for Edd and Eddy, as they seem to be sitting in a silence occupied only occasionally by the laughter of Jonny and Ed. Suddenly, Eddy leaps onto the table and starts dancing while suggesting something they can do while waiting for the others only to find that he's all alone in the kitchen again.
The four others have adjoined to the parlor. Eddy joins them there and sits down on a rug, disgruntled. Jonny runs around in circles; it seems that he's chosen to play some party games, and this one is a form of Duck, Duck, Goose he calls "Oak, Oak, Spruce". He finally chooses a spruce, but this is bad news for the game, as his choice is Plank. Jonny runs around in circles until Eddy yells for him to stop, and then nervously asks when they can have some food, only to learn that Plank supposedly ordered some pizzas. When Jonny resumes running in circles, Eddy gets more and more annoyed until he throws Plank into Jonny's head, allowing Plank to "catch" Jonny.
With Jonny downed, Eddy suggests that they crank up the tunes, but Jonny ignores him and announces a new game of trying to guess how many seeds are in a jar. Fed up, Eddy grabs Jonny by his lapels and demands to know when the others will get there so the party can finally start. Jonny then lets Eddy in on the bad news: Kevin's making cupcakes tonight, Rolf couldn't find socks that match, Nazz is pedaling papers, Jimmy had to wash his hair, and Sarah just told him to leave her alone. Annoyed, Eddy throws Jonny down and heads for the door, and when Jonny asks where he's going, Eddy tells him that the party sucks and he's leaving.
Jonny begins to weep. Hearing this, Eddy looks back at him, disgusted. Edd feels sympathy for Jonny, though, and begs his friend to stay just a bit longer. Given that it seems all that Jonny wants to do is make an Arbor Day wish, all they have to do is make the wish with him and go, so Eddy accepts. Hearing this, Jonny is instantly cheerful, and says that he was just fooling when he was crying. Jonny then sets them up to make their wishes, and immediately after the wishing is over, Ed says that he wished the party would never end and they'd party forever. Jonny tells him that that was Plank's wish too, and the three (board, baldy, and Ed) dance around, singing about how they're having a never-ending party. Eddy looks at Edd, angry, and his anger is in no way pacified when Ed and Jonny board up the doors. Suddenly, Jonny stops and puts a sapling upon the "Arbor Day acorn" and tells him that now they'll watch as this sapling grows into a fully-grown oak tree, a process which will take several decades. Eddy begs for relief and for the tree to grow when he hears this, but it doesn't seem likely that he'll get his wish any time soon.
Ed: [blindfolded for the project] "Where are you, you little dickens? Eddy? Oh! Oh! Okay, I smell cabbage, and...um, bowling shoes? Canned luncheon meat? No, wait! That is me." [Eddy lifts the blindfold from Ed's nose so he can smell.] Ed: "Peek-a-boo! I smell you!" [smells around] "I smelt it, who dealt it?"
Ed: [happy and eager] "I wish this will never end and we will party forever!"
Ed: [enthusiastically rubbing himself with his old gym bag] "Do we reek of swank or what, Double D?" Edd: [distressed] "My brain hasn't correlated that yet, Ed."
Eddy: [on the way to the party] "So, here's the drill, head for the cheese dip first. My brother told me that's where all the chicks hang out!" Ed: "Baby chickens are so cute!"
Jonny: [brandishing a gigantic jar] "New game! Plank says, 'guess how many seeds are in the jar!'" Ed: [looking at the huge jar of seeds] "Three?" Edd: [calculating avidly] "976?" [The jar slips from Jonny's hands.] Ed: [watching the jar smash on the floor] "Two?"
Eddy: "For Pete's sake, Jonny, these games stink, man! If you're gonna have a party, you gotta spice things up! Geez Louise! When's everybody supposed to get here anyway?" Jonny: "Didn't I tell ya, Eddy? Everyone said they were too busy. Kevin's making cupcakes, Rolf can't find socks that match, Nazz's peddling papers, Jimmy's washing his hair, and Sarah said, 'beat it, baldy.'"
Ed and Jonny: [chanting] "Never ending party, never ending party, never ending party, never ending party…" Eddy: "GROW YOU STUPID TREE, GROW!"
There is a poster by the gym for "Mr. Cathro's Science Class." Ken Cathro is Ed, Edd n Eddy's post-production supervisor and editor.
The music pieces Plank was supposedly playing at the end of the episode are entitled "Ode to Margot" & "Watson's Waltz." It is not known who the Watson being referred to is, but Margot is producer Dan Sioui's bulldog, who also appeared in Ed, Edd n Eddy - The Mis-Edventures as one of the enemies.
When the Eds and Jonny all move away in the scene where Plank was telling jokes, Plank did not move. In the next scene, however, has Plank disappeared from his spot. This adds to the mystery of whether Plank is a supernatural being.
Edd points out to Jonny and Plank that Arbor Day is always on the last Friday in April, which is six months from the present time. This confirms that this episode takes place in October (presumably during the second half of the month).
The music that Eddy plays at the party is the same music heard in "An Ed is Born."
Nazz and Sarah applying lipstick.
The entrance to the gym with Mr. Cathro's name on a bulletin board.
Edd getting ready to perform his experiment.
The cover sheet to the project.
Edd's science graph.
Ed trying to find the pie using only his sense of smell.