"It's a Swamp Thing" is the first segment of the twenty-second episode of 101 Dalmatians: The Series.
The episode starts with Lucky in the Colonel's rail cart, admiring the images of the many campaigns which the Colonel has taken part in. He particularly admires the regimental scarf which the Colonel wears, thinking he'll look great in it. The Colonel allows him to wear the scarf for the day, and Lucky admires it in a mirror. Cadpig, Rolly and Spot arrive so Lucky can join them to look for rocks, but Lucky then notices an image of the swamp. The Colonel also explains that others call it "The Widow Maker", "Satan's Punch Hole", and "El Perdito", and he advises the pups not to ever step paw in the swamp.
Lucky, however, gets Cadpig, Rolly and Spot to come with him to the swamp, seeing it as an adventure, but the others try to obey the Colonel's advice. As Lucky tries to convince them, the scarf slightly drops into the water where Swamp Rat is swimming. Swamp Rat uses the scarf as a towel before he pulls it from Lucky's neck.
Seeing where Swamp Rat took the scarf, Lucky finds a fishing line and uses Spot as a lure to try and get the scarf back. This results in Spot fishing out a boot, getting covered in mud, and then reeling in a muffler, which causes the Dalmatians and Spot to get tangled in a tree.
The Dalmatians and Spot then head in to the swamp. Rolly reminds Lucky that the Colonel told them not to step paw in the swamp, but Lucky explains that they're not "stepping" but "wading". They arrive at the entrance of Swamp Rat's store, and he tries to sell them a color television...knob, a washer/dryer...vent, a kitchen sink...faucet, and then a '57 Chevy muffler (Lucky explains, they already have one), but Lucky asks about a scarf, and Swamp Rat invites them in to discuss it over a "friendly game of chance."
Inside Swamp Rat's store, he plays a shell game with them. Lucky thinks he knows where it is, but he picks the wrong shell (or more likely, Swamp Rat cheats) and Swamp Rat takes the Dalmatians' collars. Swamp Rat offers for them to play again, but Lucky insists where they can get the Scarf. Swamp Rat explains that he sold it to Cydne the water snake.
The Dalmatians and Spot head to the snake pit, where Spot insists that she does the talking. They summon Cydne and when Spot tries to explain what is up, Cydne thinks they're solicitors and goes back inside. While Rolly feels defeated, Lucky insists that they're not giving up. Cadpig feels tension too, and gets Spot to summon Cydne again. When Cydne reappears, Cadpig claims that she thinks that the snake needs a group hug. Cydne plays along using the "hug" as a means to constrict the Dalmatians and Spot. As he does so, Cadpig is able to ask him about a scarf, with Cydne explaining that he sold it to Steven. Cydne constricts them so hard that he accidentally launches the Dalmatians and Spot to safety, while getting himself in a knot.
The Dalmatians and Spot land in a pile of mud with Rolly angry at Cadpig for what her plan had almost caused. Lucky notes that they need to find Steven, and Spot notices a sleeping Steven wearing the Colonel's scarf. Lucky claims that he'll get the scarf, but Spot insists that she'll get it. Spot is able to sneak around Steven and get the scarf on her, but then she yells out that she got it, causing Steven to wake up and snap Spot into his muzzle.
Lucky is able to rescue Spot, and the alligator chases the Dalmatians and Spot through the swamp. During the pursuit, they interrupt a poker game that Swamp Rat is playing, causing the rat and his playmates to be sent flying. Steven then chases the Dalmatians and Spot into a tree, but the alligator soon gets stuck.
The Dalmatians and Spot are able to escape the swamp, but see that the Colonel's scarf is practically a muddy wreck. Lucky claims that he knows how to handle the Colonel and, if they act natural, the Colonel shall never know. Though as they approach the Colonel's carriage, it shows the Dalmatians and Spot haven't any fur (or feathers) on their tail sides.
The Colonel is instantly able to tell that the Dalmatians ignored his warning, and questions why they disregarded his advice. Lucky insists it was for a good reason and points out that it was to get the scarf back. However, the Colonel shows that he has an entire trunk full of regimental scarves. The Colonel explains that while a scarf may be able to be replaced, the Dalmatians cannot. He then consults with Sergeant Tibbs about a suitable punishment.
Sgt. Tibbs feels that they are a younger generation, so they are free-willed and prone to thrill seeking. The Colonel admits that it's a lesson they've all had to learn, showing that he and Sgt. Tibbs are also missing the fur from their tail sides, likely suggesting that they too did something similar to what the Dalmatians and Spot had done.
- This episode is supposed to mark the introduction of the swamp and those who live there in 101 Dalmatians: The Series, but because of airing issues, we first meet Swamp Rat in "Two for the Show".
- The Colonel's images look a lot like famous images of history. One called the "Great Gruteley Kibble Kaper" looks like the "Raising the Flag on Iwo Jima" image; and the infamous "Flea Bath Uprising" image looks like the "George Washington's crossing of the Delaware River" image.
- This is one of four episodes that contain laugh tracks that play when a character says a comedic one-liner; the other three being "You Slipped a Disk", "Chow About That?", and "Walk a Mile in My Tracks".
- Swamp Rat tries to sell the Dalmatians a muffler to a '57 Chevy.
- Despite the pups getting the scarf back from him, Steven still has the scarf in later episodes. Though it is possible that he somehow stole it back from the Dalmatians.