The episode begins in the desert, where Knuckles drives a monster truck while Sonic and Tails, who are hanging onto enerbeams, travel behind him on hoverboards. Knuckles is about to go into maximum overdrive, when the monster truck's built-in oven dings. Knuckles' slice of pizza is cooked, and the heat of the pizza causes Knuckles to lose control of his monster truck. He drives it straight into Hedgehog Village, where Lady Walrus is pushing a baby carriage with her infant son, Chumley, inside it. Knuckles screeches his monster truck to a halt, and it crashes into a tree. Tails is relieved that no one got hurt, but the tree falls on Lady Walrus as she tries to get out of the way of it.
A few minutes later, Sonic, Tails, and Knuckles apologize to Lady Walrus, who is in the hospital. Tails suggests that they, as a culture, ban the use of built-in pizza ovens from motor vehicles. Lady Walrus asks the Doctor if she'll be able to walk to Meh Burger Again, and much to her disdain, he tells her that she will. The doctor then tells her that she will need her rest, and can't get out of her bed for the next few days. Stratford, Lady Walrus' older son, volunteers to take care of Lady Walrus until she's healed, and while Lady Walrus is relieved to hear that, she wonders who will take care of Chumley. After questioning why she suddenly cares for the safety of her children, Tails convinces Sonic that they and Knuckles can look after Chumley. Sonic figures that since they save the village on a weekly basis, it shouldn't be too hard to look after a baby.
At Sonic's house, Chumley won't stop crying. Tails tells Knuckles that Chumley must be hungry, so Sonic suggests that they feed him a chili dog. Tails tells Sonic that babies like Chumley can't eat solid food yet, so Sonic tells Tails to put it in the blender. Knuckles misinterprets this, and holds Chumley over the blender, until Sonic tells him he was talking about the chili dog. After blending the chili dog, Knuckles attempts to spoon-feed it to Chumley, but gets too caught up in pretending the spoon is an airplane, upsetting Chumley. After Sonic scolds Knuckles for fooling around, Knuckles finally feeds Chumley. Sonic tells Tails and Knuckles that taking care of a baby isn't so hard, but unfortunately for them, Chumley dirties his diaper.
Sonic, Tails, and Knuckles stop by Amy's house, where Amy outright refuses to change Chumley's diaper for them. Sonic tries to convince Amy that somebody other than him, Tails, and Knuckles have to be responsible for their actions, but Amy tells them that since they're the ones looking after Chumley, they have to change his diaper.
At Tails' workshop, Sonic, Tails, and Knuckles dress in space suits as they change Chumley's diaper. Unfortunately, not long after they change Chumley's diaper, Chumley dirties it, and now they have to change it again.
Later that day, Chumley will not stop crying and go to sleep, even though he's been both fed and changed. Tails suggests that he, Sonic, and Knuckles sing a lullaby. Sonic tries to do so, but his speed, combined with his ire, does not succeed in doing the job. Knuckles suggests to Sonic that they put on more of a show, so they and Tails dress as their Dude-itude band and sing a rock lullaby. Unfortunately, this still doesn't succeed in doing the job. After Knuckles tells Tails that they have to pack their suits back into the Dude-Mobile, Tails gets the idea to make a mobile for Chumley. The mobile Tails makes calms Chumley to sleep, much to Sonic, Tails, and Knuckles' relief. Sonic asks Tails how he knew the mobile would work, and Tails tells Sonic that studies show that the motion and sound of mobiles appeal to an infant's simple and underdeveloped mind. The mobile also succeeds in putting Knuckles to sleep, due to Knuckles' equally underdeveloped mind. Sonic tells Tails that Chumley is cute when he isn't screaming his head off, but all of a sudden, an explosion awakens Chumley. Sonic, Tails, and Knuckles all rush outside, and find an army of Badniks outside Sonic's house. Sonic asks Knuckles to look after Chumley while he stops the Badniks. As Sonic and Tails destroy the badniks, Knuckles bottle-feeds Chumley. Sonic then confronts Eggman and scolds him for waking Chumley up when they finally got him to sleep. Eggman retaliates by tossing Sonic at Knuckles, knocking Chumley out of his arms. Fortunately, Tails catches Chumley before he can hit the ground. After Knuckles takes out an army of Crab Bots, a bee bot shoots Chumley out of Tails' arms, causing Chumley to land in Eggman's Eggmobile. Chumley then presses various buttons on the Eggmobile, disabling the control over it and the badniks. Sonic then takes Chumley back from Eggman, and Knuckles kicks the Eggmobile away. Sonic praises Chumley for helping him, Tails, and Knuckles defeat Eggman, and Tails realizes that all Chumley wanted was some gratuitous violence, and Knuckles says that Chumley is a baby after his own heart.
Sonic, Tails, and Knuckles walk through Hedgehog village, with Knuckles carrying Chumley in a baby carrier, and Sonic testing the temperature in Chumley's bottle. Tails bottle-feeds Chumley, and this earns him, Sonic, and Knuckles the awes of Perci, Staci, and Zooey. Sonic, Tails, and Knuckles then go to the Male Fennec's shop and buy Chumley a stuffed giraffe. Sonic then takes Chumley for a ride and runs around the well. Later, at Sonic's house, as Sonic plays with Chumley, Tails cooks dinner while Knuckles walks in, wearing a business hat and carrying a briefcase. Knuckles tries to sleep on the couch, but Tails hands him a garbage bag to take out. Knuckles growls in retaliation, which upsets Chumley. Knuckles later cheers Chumley up by pushing him on the swings, but he pushes the swing too hard and launches Chumley into the air. Fortunately, Sonic catches Chumley before he can hit the ground. Tails then takes Chumley for a ride in his plane. At the end of the day, Sonic, Tails, and Knuckles are all exhausted from a hard's day's work babysitting, and they, along with Chumley, all fall asleep.
The next morning, Knuckles wakes up and asks Sonic and Tails where Chumley is. Much to their horror, Chumley isn't in his carriage. Sonic tells Tails and Knuckles not to panic, and they look all over Sonic's house, but all they find is Chumley's stuffed giraffe, indicating that Chumley has run away. Sonic, Tails, and Knuckles realize that Chumley might be in danger, and set off to find him. Sonic suggests that he, Tails, and Knuckles look in every dangerous place in town, so they start with the volcano. After getting scorched by the lava, Sonic realizes that Chumley isn't there. Knuckles then checks a coconut tree by kicking at it. Nothing falls out, so Knuckles suggests that nothing is in the tree, only for five coconuts to fall from it and land on him. After Tails and Knuckles check the desert, Sonic decides the one last place they should check the most dangerous place of all; Meh Burger. At Meh Burger, Dave assures Sonic, Tails, and Knuckles that no babies have come here all day, and Sonic, Tails, and Knuckles all hug each other and Dave in relief upon hearing this. Sonic then realizes that even if Chumley isn't at Meh Burger, he, Tails, and Knuckles still have to tell Lady Walrus that Chumley is gone. After remembering the good times they had with Chumley, Knuckles begins to blame Sonic for not installing a door on his house and not securing Chumley in a safety hammock. Sonic then tells Knuckles that he's also partially responsible for losing Chumley, and Tails realizes that all three of them are equally responsible, which means they should all tell Lady Walrus the bad news together.
At Lady Walrus' house, Lady Walrus has made a miraculous recovery. As Sonic and Knuckles try to tell her that Chumley went missing, but then Tails points out that Chumley is walking on the roof, and much to his, Sonic, and Knuckles' relief, Chumley is just fine, apart from being about to fall off a roof. Fortunately, Tails catches Chumley before he hits the ground. Lady Walrus is happy to see Chumley again, and thanks Sonic, Tails, and Knuckles for taking care of him. Sonic tells Lady Walrus that it was no trouble, and Knuckles says good-bye to Chumley, encouraging him to lift weights. He then starts crying, and Sonic and Tails calm him down.
Later that day at the desert, Amy asks Sonic, Tails, and Knuckles if they've learned a valuable lesson from their ordeal, and Sonic assures her they got a crash course in responsibility. Tails then tells Amy that he installed a throttle on the pizza oven in Knuckles' monster truck, so that the oven will only work in park mode. Amy scoffs unamused, and as Knuckles gets into his monster truck, he tells the viewers not to cook and drive. He drives away, with Sonic and Tails in tow, much to Amy's ire. As the episode ends, Chumley's stuffed giraffe is revealed to be hanging from the rear-view mirror.
This episode provides examples of:
- Absentee Actor: Sticks does not appear in this episode.
- Accessory-Wearing Cartoon Animal: Invoked; when the slice of pizza lands on Knuckles' leg, it burns it and causes Knuckles to lose control of his monster truck. Knuckles then exclaims, "It's days like these I wish I wore pants!".
- Adult Fear: While they're not quite adults, Sonic and Tails are shocked when Knuckles asks them where Chumley is and they find out he ran away.
- Babysitting Episode: Sonic, Tails, and Knuckles get a job babysitting Chumley in this episode.
- Badly Battered Babysitter: When Chumley runs away, Sonic gets scorched looking for him in the volcano, and Knuckles gets hit with coconuts looking for him in the coconut tree.
- Knuckles' careless cooking pizza while driving him causes him to swerve towards Lady Walrus. He doesn't hit her with his monster truck, but he does hit a tree... which doesn't fall on Lady Walrus until after Tails says, "Wow! That was lucky! Somebody could have gotten hurt!"
- When Chumley runs away, Knuckles checks a coconut tree by kicking at it. After he kicks it, nothing happens. Then after Knuckles kicks at the tree, he says, "Nope, nothing in the tree", and five coconuts fall on his head.
- Black Comedy: While the guys are attempting to feed Chumley, Sonic suggests they give him a chili dog, but Tails informs him that the baby can't eat solid foods, so they decide to put the chili dog in the blender. Knuckles misinterprets this, however.Knuckles: Well, if you say so. (holds Chumley over the blender)
Sonic: The chili dog, not the baby!
Knuckles: Oh, okay. That makes more sense.
- Book-Ends: This episode begins and ends with Knuckles driving his monster truck through the desert, with Sonic and Tails in tow.
- Coconut Meets Cranium: After Knuckles kicks a coconut tree to check if Chumley is in there, five coconuts fall on him, though not immediately after he kicks the tree.
- A Day in the Limelight: For Chumley, the infant son of Lady Walrus.
- The Diaper Change: When it comes time to change Chumley's diaper, Sonic, Tails, and Knuckles try to talk Amy into doing it for them, but she outright refuses, and insists they do it themselves. They all do so themselves, dressed in space suits. Unfortunately, not long after they change Chumley's diaper, they have to change it again.
- Idiot Plot: Knuckles' attempt to drive his monster truck and cook pizza at the same time is what sets this episode's plot in motion.
- Manchild: The mobile Tails makes not only helps Chumley fall asleep, but Knuckles as well.
- Medium Awareness: When Sonic volunteers himself, Tails, and Knuckles to babysit Chumley, he mentions that they save the village on a weekly basis.
- Mystery Meat: When Sonic, Tails, and Knuckles find out that Chumley didn't go to Meh Burger when he ran away, Sonic tells Dave it's great that Chumley is not ingesting Grade-D beef. Dave then tells Sonic, "I wouldn't call it beef, per se."
- Mythology Gag: This isn't the first Sonic cartoon to have an episode referencing Three Men and a Baby. Both episodes also have Sonic trying to feed a chili dog to a baby.
- Never My Fault: When Chumley goes missing, Knuckles tries not to play the blame game, but blames Sonic for not installing a door on his house and not securing Chumley in a safety hammock.
- Nice Job Breaking It, Hero!: Knuckles' cooking while driving injures Lady Walrus.
- Papa Wolf: Sonic, Tails, and Knuckles are clearly angry at Eggman when he wakes up Chumley.
- The Reveal: The names of Lady Walrus' children are revealed in this episode; her older son is named "Stratford", and her younger son is named "Chumley".
- Safe Driving Aesop: Spoofed; The plot is started by Knuckles being distracted by the pizza oven in his monster truck, which leads to Lady Walrus getting injured. At the end of the episode, Tails solves this problem by making it so that the oven can only work in park mode. Knuckles then informs the viewers not to cook and drive.
- Shout-Out: This episode's title is a reference to the 1987 movie, Three Men and a Baby.
- Spoof Aesop: When Amy asks Sonic, Tails, and Knuckles if they've learned a valuable lesson from their ordeal, Sonic tells them they have, and Knuckles tells the viewers, "Don't cook and drive!".
- Straying Baby: Chumley runs away from Sonic, Tails, and Knuckles near the end of the episode, and Sonic, Tails, and Knuckles look everywhere they can for him.