The episode begins with the Tennysons arriving at their family reunion in the Rustbucket. Max tells Ben and Gwen to stay on their best behavior, and not to have a repeat of last year. A brief flashback is shown, where Ben and Gwen have a burping contest, which eventually leads to the gazebo they're in falling down on them. Ben walks up to his extended family with the deviled eggs Max cooked. His uncle Bob tells him they're watching him, and not to break anything. Aunt Cathy comes up to Ben, telling him that she strongly opposed to inviting his family back this year. She then hugs Ben, and asks him how he's doing. She then leaves to have some of the deviled eggs. Ben walks upt to Max, who is laughing alongside some other family members. Max tells Ben that it really brings back memories. Ben questions if he knows all of these people, and Max introduces him to the various members of the Tennyson family. Another family member, Alfred , walks up to them. Max and him shares some laughs. Max tells Ben that Alfred Lord Tennyson is his second cousin.
Elsewhere, Ben and Gwen's great-grandma Rita shows Gwen pictures of Max in his youth. Max and Ben walk up to them, and Max is embarrassed by the photos of him as a teen. Rita leaves to find more photos of Max. Max tells his grandchildren that, so far, they are doing great. Ben leaves to go get some deviled eggs, but he notices Kevin, who is eating food. Ben confronts him, telling him that those eggs don't belong to him. They prepare to fight, but Gwen intervenes, and tells Ben to bring the fight elsewhere, away from the reunion. They leave for the nearby park. At the park, Ben transforms into Four Arms, and Kevin transforms into Crystalfist. Aunt Cathy hears a noise, but Max convinces her it's raccoons. He then tells Gwen to go see what's going on. Four Arms manages to outmatch Crystalfist, and sends him flying into the air. As they continue to fight, he takes the trunk of a tree, and bats Crystalfist across the park.
Ben times out, and leaves to go hide somewhere. He finds and jumps into a dumpster. In there, he finds the Bugg Brothers. Ben questions what they're doing there. Maurice states that they're there to test out his latest invention. Maurice demands Sydney to hand him something, which Sydney obliges to. Maurice introduces Ben to the particle decimator. Maurice explains that it is a shrinking ray. While he talks, Ben transforms into Heatblast and escapes from the dumpster. Maurice hits Heatblast with the machine's rays, however, and it instead functions as a head-swapping device. Heatblast finds his head on Maurice's body, and Maurice's head on Heatblast's body. Maurice is confused, as it was not the shrinking ray. He instructs Sydney to grab the Cranium Displacer, and Sydney nabs it from Heatblast. Crystalfist returns, and insults Heatblast for his head being swapped. Crystalfist's head is then swapped with Sydney's. Maurice demands Crystalfist to hand it over. Crystalfist questions who he is, and why he made a head-swapper. Maurice explains that it's one of his earliest inventions, and that he was going to unveil his latest creation, until Sydney brought the wrong device. Sydney and Maurice surrounds Crystalfist.
Heatblast wakes up, and notices Crystalfist. He attempts to use his powers, but he realizes his body is still swapped. Sydney and Maurice tackles Crystalfist, and the helmet flies into the air. Heatblast runs towards it, and attempts to catch it. He grabs it, but is soon hit by Maurice's newfound pyrokinetic powers and drops it. Gwen arrives, and Heatblast tells her to get the helmet. She dons the helmet and fires it off, but Sydney deflects it, making it hit Max, swithcing their heads. Crystalfist and Heatblast both time out. Ben grabs the helmet, and tries to find the off switch. Kevin takes it, and switches heads with Maurice, putting Kevin's head on Ben's body, and Maurice's head on Sydney's body. Ben runs away with the helmet, but Sydney tackles him, and it fires off. A squirrel is caught in the blast, swapping bodies with Ben. Kevin once again picks up the helmet, as an attempt to switch his head back. Maurice takes it from Kevin, and uses it to switch his head back. Maurice returns to his bug-like body, however, the squirrel on Sydney's body has the device, and gnaws on it, causing it to malfunction.
The helmet begins affecting everyone, switching their heads seemingly at random. Eventually, Sydney's head is back to normal, as well as Maurice's. Kevin threatens Sydney, holding Maurice in his hands and donning the helmet. He questions how he gets back to normal. However, Kevin can't understand Sydney's gargling. Sydney and Maurice then begin to argue. Ben, in Kevin's body, from behind a tree, hopes for them to take each other out. He then gets a call from the Forever Knight, telling Kevin to report back. Ben pretends to be Kevin, and tells him that he is hanging around with family. Forever Knight scoffs, stating that he has no family, and without him, he has no one. Ben figures that it might've been the reason Kevin came to the reunion, as he just wanted to be around a family.
Kevin insults the Bugg Brothers, finding their shrinking plan dumb. Ben yells out, telling Kevin to switch them back. Kevin gladly does so, fixing them. Maurice asks for the helmet back, however, Ben transforms into Rath and destroys it. Rath threatens them with his sharp claws, so Maurice and Sydney run away. Rath looks around for Kevin. Meanwhile, Kevin walks away from the scene. Gwen runs up to Ben, asking what happened to the helmet, since Max is still stuck on a squirrel's body. Rath looks down at the destroyed pieces.
Later, Aunt Cathy says her goodbyes to the Tennysons as they sit in the Rustbucket. Max tells Gwen to plug in the address for Phil's house, since he can fix their issue. Max checks if everything is okay with his body. Ben tells him that the squirrel on Max's body likes the deviled eggs, so he won't get out of control.
Grandma Rita: Whoo! And here is your grandpa Max siting on Santa's lap. (Shows another picture). Gwen: Ah! Grandma Rita: Yeah, that handsome baby grew into the most awkward-looking teen I'd ever seen! Max: Oh, what's Grandma Rita -- Oh! Oh! I thought those were destroyed! Ben: (Laughs). Gwen: Have you always worn Hawaiian shirts? Max: What? The material really breathes!
Gwen: Well, so far, so good. Right Grandpa? Max: You kids are doing great. Ben: See? It's all good. Now to get some of them deviled eggs...(Groans). What is he doing here? Gwen: You don't think he's related to us, do ya? Max: Now, Ben, don't do anything rash. Ben: What? I'm just gonna say hello. Kevin, that egg doesn't belong to you. Kevin: Come and get it. Ben: I think you should leave. Kevin: You really want to do this here? Ben: You bet I do! Gwen: Ben! Ix-nay with the ouble-tray. Perhaps you'd like to show your friend Kev the big empty park over there. Ben: Okay! Come on Kev. Let's go see the park.
Maurice: Allow me to introduce you to... the particle decimater! Ben: Kind of looks like a bonnet. Maurice: A bonnet? Please! This, my feeble friend, is a shrinking ray. With this, I'll destabilize the national economy, undermine the government, disrupt social order, and wreak havoc upon everyone in the world. Countries will bow before me. No more waiting in likes for coffee!
Maurice: Drop the helmet! Crystalfist: Helmet? It looks like a bonnet. Maurice: It's a cranial displacer! Crystalfist: (Blinks confused). Maurice: A head-swapper, and I would like to have it back. Crystalfist: Who are you, and why would you make a head-swapper? Maurice: I am Maurice, and that is one of my earliest experiments. I was going to unveil my latest creation, but Sid over here brought the wrong device. Crystalfist: Who's Sid? Sydney: (Grumbling). Crystalfist: Hey, his head is on my body.
Kevin: Cool it, cockroach. I suggest you keep those arms nice and high. Now, how do I get myself back to normal? Sydney: (Squeaking). Kevin: What? Maurice: Don't listen to him. Sydney: (Squeaking). Maurice: You're the one that got us into this mess! Ben: Boy, nothing would make me happier than to see those loser take each other out. (Phone rings). Huh? Forever Knight: Kevin, where are you? We have work to do. Ben: Uh, hey, jerk-face. I'm, uh, just hanging with my family. Whatevs! Forever Knight: Family? (Scoffs) That's a laugh. You have no one. Without me, you're all alone, remember? Now, stop playing around and report back here at once. Ben: No family? Could that be the reason he crashed my reunion? he just wanted to be around family?
Kevin: So your plan to destabilize the world was to shrink stuff? Are you both brainless? Sydney: (Squeaking). Maurice: (Laughs). You tell him, Sid! Ben: Kevin! If you want your body back, you just have to blast me with the... Kevin: Okay!
This episode was aired on October 7, 2019 in Germany.[1][2]
Despite this episode taking place at a family reunion, Ben and Gwen's parents do not appear, nor are mentioned in this episode.
This episode chronologically takes place before Roundabout as Kevin is not yet trapped between space and time.[DR 1] This is because new episodes were ordered at the last minute.[DR 2] The extra season 3 episodes were supposed to be spread throughout the season.[DR 3]