How Much is That Gorilla in the Window?
Mario and Pauline are chasing after Donkey Kong who escapes on a ladder. Mario tries to follow, but Donkey Kong simply throws some barrels at him, knocking him down. Donkey Kong then falls through the vent of a building and falls onto the first floor, which is a pet store. At the same time, a limousine pulls up near the pet store, and the two escorts, Solmes and Kenworth, drop off a boy named Brian there. They then secretly discuss their plan to steal the mansion from Brian's family.
As Brian navigates the pet store, Donkey Kong sneaks around. As he lets out a fellow gorilla from its cage, he notices a Banana Bunch, and starts eating it. Brian spots him and, immediately falling for Donkey Kong, "purchases" him. After a brief introduction, Brian and Donkey Kong head to the limousine, where a shocked Solmes and Kenworth await. Donkey Kong barely fits into the limousine, and so upon Brian's wishes, tears off part of the limousine to turn it into a convertible. Kenworth drives away while an equally shocked Mario and Pauline watch.
Brian celebrates his birthday with Donkey Kong. Solmes and Kenworth attempt to create a diversion to steal Brian's family's jewels, the only way they can acquire the mansion, but Donkey Kong blows out the candles of Brian's cake too strongly, drenching Kenworth in the cake's icing. Solmes sends Kenworth away to clean himself off, and gives Brian a bike for his present. He and Donkey Kong begin taking it for a test drive.
Kenworth opens the safe the steal the jewels, only for Brian and Donkey Kong to crash into him on the bike. When Brian questions Kenworth as to why the safe is open, Kenworth claims that a "burglar" tried to steal the jewels, but he "stopped" the burglar. Brian and Donkey Kong decide to track the burglar in case he "comes back". Realizing that Donkey Kong is hindering their progress, Kenworth suggests to Solmes calling the local zoo to spread a hoax that Donkey Kong is an "escaped animal".
As Kenworth makes the call, Brian and Donkey Kong spot him and find out what he is up to. Angered by Kenworth's deception, Brian fires him and orders Donkey Kong to boot him out the front entrance of the mansion. Solmes pretends to congratulate Brian, then confronts Kenworth and demands that he must sneak back into the mansion at all costs if he wants a share of it as well.
Not too long after, Mario and Pauline arrive at the scene and, spotting Kenworth attempting to sneak into the window, ask him about Donkey Kong's whereabouts. Kenworth deduces that they are from the local zoo (rather than the circus) and demands Mario to capture Donkey Kong. Mario and Pauline then disguise themselves as "Acme Laundry" employees (and disguise their circus van accordingly). Brian also deduces that they are "the nasty zoo guys". Mario then tricks Donkey Kong into being captured, but Brian cuts him free. Donkey Kong then puts the sack Mario is dragging onto a statue to trick Mario into dislodging it, causing him to be washed away by some unplugged water. As Brian and Donkey Kong escape back into the mansion, Pauline notices that they can fit into the ventilation system, and she and Mario do just that.
As Brian points out his family's jewels to Donkey Kong, Solmes and Kenworth watch from behind the door and devise a new plan. Mario and Pauline, eavesdropping on both parties, devise a plan themselves. As Brian and Donkey Kong head out to a nearby golf course, Solmes and Kenworth begin pouring concrete as a trap. Mario, enacting his own plan, enters the novelty windmill. After Brian putts a hole-in-one (with some assistance from Donkey Kong), Donkey Kong putts, he hits the windmill, causing it to fly towards him. Mario attempts to net him, but Donkey Kong simply jumps over the windmill, causing Mario to lose his balance and fall. Donkey Kong then throws bowling balls at Mario, causing him to fall into the concrete trap. Pauline cries for assistance, and Donkey Kong attempts to jump in to rescue Mario, only to also fall into the concrete trap. Solmes and Kenworth then steal the jewels, causing Brian to realize who the real culprits are.
Solmes and Kenworth then escape into a closet and put on some ape costumes to create another diversion. Though Mario and Pauline are fooled by the costumes, Brian and Donkey Kong are not. Brian throws out some bowling pins, while Donkey Kong throws a bowling ball, ejecting the villainous duo out the front entrance. They are then netted and driven away by the same zookeeper Kenworth called earlier.
Mario then chains Donkey Kong to send him back to the circus. When Pauline asks how Brian will deal with Donkey Kong leaving, Mario says that it won't be a problem, pointing to Brian, who is now speaking to a girl about the climactic events. Brian does, however, give some credit to Donkey Kong for helping, cheering him up. Donkey Kong then breaks free and wraps the chain around a lamp post, shocking Mario. He then playfully rides away on Brian's bike.