Never Koop a Koopa

Never Koop a Koopa is the sixth episode of The Adventures of Super Mario Bros. 3; it aired alongside another episode of The Adventures of Super Mario Bros. 3 entitled "Princess Toadstool for President".

Plot
Mario, Luigi, Princess Toadstool and Toad are eating pasta for lunch outside of Toad's House. Mario looks around. "Wha? Impossible! King Koopa's throwing in the towel?!? It is the sight of Bowser and the Koopalings, who are walking towards them, holding a white flag. To the surprise of Mario and his friends, Bowser announces that he's giving up his evil ways, and is leaving the Mushroom Kingdom forever. To try and make up for all the misery that he's caused, he gives Princess Toadstool the key to Castle Koopa as a donation to charity. Bowser then uses his Magic Scepter to create a Warp Pipe which he and his kids exit through.

With the key to Castle Koopa now in her hands, Princess Toadstool figures that she can turn the place into a retirement home for elderly Mushrooms. Luigi warns Princess Toadstool that the whole ordeal is probably a trap, and tells her to throw the key away. However, Princess Toadstool points out that the old people of her kingdom need a good home, and decides to visit Castle Koopa right away. Mario tells Luigi that he'll travel with Princess Toadstool to protect her, just to be safe. Princess Toadstool and Mario then head for the Warp Pipe to Dark Land, while Luigi and Toad follow along.

Upon unlocking the front door to Castle Koopa, Princess Toadstool and Mario are greeted by a falling Dry Bones. Princess Toadstool figures that they'll just need to clean the place up a bit, but Mario, suspecting danger, decides to enter first. In the front hallway, Mario and Princess Toadstool pass by portraits of the Koopas; the moving eyes of Bowser's freak Mario out. After Princess makes a remark about Bowser's portrait being the first thing to go, the front doors suddenly shut.

A Thwomp near the ceiling taunts Mario and Princess Toadstool, and comes close to crushing them. Mario and Princess Toadstool run towards the other end of the hallway, dodging several more Thwomps. Two Ptooies come and attack Mario, but he deflects their balls with his plunger, allowing him and Princess Toadstool to slip past them. After running down a few more corridors, Mario and Princess Toadstool stop to count their steps, when a trapdoor opens beneath them, dropping them to the dungeon.

Standing outside the door to the dungeon are Bowser and Cheatsy. Bowser mocks his new guests, and Princess Toadstool comments that she never should've trusted him. Bowser tells Cheatsy that he's going to give him more lessons on lying and cheating, but his son doesn't hear him, as he's listening to a walkman. It isn't until he pulls the headphones off of Cheatsy's head that Bowser gets his son's attention. Bowser then tells Cheatsy to pay attention while he cons Princess Toadstool out of the Mushroom Kingdom. Bowser presents a contract to Princess Toadstool, but she refuses to sign it. To help get Princess Toadstool to change her mind, Bowser pulls a lever, releasing about 25 Bob-ombs into the dungeon. Knowing that Princess Toadstool and Mario are trapped with the Bob-ombs, he figures that they'll surrender soon.

Meanwhile, Luigi and Toad are waiting in a boat outside Castle Koopa (possibly on the Mushroom Sea). Toad comments that Mario and Princess Toadstool have been inside too long, and that they should go and investigate. Luigi then points out that they'll have to sneak in through the drainpipe. Thinking that Luigi was being sarcastic, Toad is startled when the plumber gets ready to jump in the water, bringing him with him. Luigi manages to swim past several Bloopers, but only Toad notices the Boss Bass that's chasing them. As Luigi unscrews the grating on the drainpipe, Toad points out the Boss Bass to him, scaring him into unscrewing the grating faster. Luigi and Toad manage to enter the drainpipe right before the Boss Bass reaches them.

Back in the dungeon, Cheatsy mentions that he likes his father's "Big Bang" theory, and Bowser remarks that in order to be a big cheat, one needs to double-trick, double-deal and double-cross. The double-cross bit gives Cheatsy an idea, but he keeps it to himself.

In another part of the castle, Luigi and Toad enter through a manhole in the floor, only to be greeted by two Sledge Bros. Luigi and Toad try to run away, but the Sledge Bros. pound the floor, causing them to fall over. Luigi and Toad are then caught and get thrown in the dungeon, just as the Sledge Bros. pull Princess Toadstool out.

Bowser tells Princess Toadstool that her friends will be blown up if she doesn't sign over the kingdom, and she agrees, on two conditions. One: That they move to the throne room. Two: That King Koopa puts on something formal to wear.

Bowser tells Cheatsy to take Princess Toadstool to the throne room while he finds something to wear. Cheatsy then thanks Bowser for his lesson in cheating, and his father says that one day he'll be just as big a cheat as himself. As Bowser walks off, Cheatsy comments to himself that that day will be today, and orders the Sledge Bros. to take the prisoners to his bedroom, where Mario, Luigi and Toad get locked in his wardrobe. Cheatsy tells Princess Toadstool to sign the kingdom over to him, or else he have her friends sent back to the dungeon with the Bob-ombs.

Princess Toadstool signs the contract and hands it over to Cheatsy, who gets so ecstatic over the whole deal that he runs off to tell his father that he double-crossed him. With Cheatsy gone, Princess Toadstool breaks a lamp, causing the Sledge Bros. to come running in. Princess Toadstool dodges their sledges, which hit and break open the wardrobe, freeing Mario, Luigi and Toad.

The four heroes run out of Cheatsy's bedroom dodging the attacks of the Sledge Bros. As they continue down the hallway, they are attacked by two Fire Chomps. Mario and Luigi take care of the Fire Chomps by pushing them out a window, and they fall down into the water. Looking out the window, Toad comments that they'd be free if only they could fly. Toad's comment then gives Mario the idea to start bashing the blocks in the ceiling, in hope that he'll find some Super Leaves.

At the same time, Bowser enters the throne room wearing a red cape, but Cheatsy comes running in and sits down on the throne. Bowser yells at Cheatsy, but Cheatsy tells him that he's the new king of the Mushroom Kingdom. Cheatsy shows Bowser the contract and takes his crown, telling him that he can get a job cleaning the royal stables, as a reward for giving him the idea to cheat in the first place.

Having read the contract thoroughly, Bowser takes back his crown, and points out the flaw in Cheatsy's plan: Princess Toadstool drew a goofy face instead of actually signing the contract. Bowser claims that he'll get Princess Toadstool to sign the contract properly, and asks Cheatsy where the prisoners are. Cheatsy tells him that they're locked in his bedroom, but they're both surprised to see Mario and his friends, all with Raccoon Power, flying outside the windows to the throne room.

Unable to stop the good guys, Bowser starts growling at Cheatsy, who tells him that he was only doing bad like he taught him. Bowser then starts chasing Cheatsy around the throne in circles, telling him that he's really going to teach him a lesson now.

Trivia

 * Although completely coincidental, Bowser bears a great resemblance to King K. Rool while wearing his red cape.
 * This is the only Mario cartoon to show alcohol usage. Mario and his friends drink wine with spaghetti.
 * The opening curtain title screen used for this episode is Dark Land, yet the Grass Land music is played with it.
 * The song Cheatsy listens to on his walkman is the underground theme.
 * When Cheatsy is talking to Bowser while sitting on the throne, his snout keeps flipping from white to orange.