At Mario Brothers Plumbing, Mario and Luigi are in the middle of fixing up a bizarre-looking contraption made of springs when Luigi tells Mario to get the door. As Mario walks towards the door, he hears the doorbell ring and ponders on how Luigi even knew that someone was there. Luigi asks Mario if he's expecting anybody, only for Mario to say that he hopes that it isn't "that magazine guy".
When Mario opens the door, he is greeted by Inspector Gadget, who tells the brothers that he is under the impression that they can fix anything mechanical. Inspector Gadget notes that he needs an emergency adjustment and then formally introduces himself. As Mario shakes Inspector Gadget's hand, he accidentally pulls off Gadget's hammer. Mario agrees to fix his gadgets and asks Inspector Gadget to come back in an hour, but Inspector Gadget explains that his gadgets need to be fixed while he waits, for he is awaiting important instructions from "the Chief". Luigi points out that the Chief is calling just before Inspector Gadget's gadget phone starts ringing. Inspector Gadget has a brief conversation with the Chief and tells him that he'll be over as soon as the Mario Bros. fix him up. When Inspector Gadget tries to retract his phone antenna, he breaks it and exclaims that he's going to pieces.
A few minutes later, Inspector Gadget is lying down on an assembly table, while Mario and Luigi have donned scrubs. "Dr. Luigi" asks "Dr. Mario" if he's ready, which he affirms, and the two stick cotton balls in each other's ears. When Mario asks why they just did that, Luigi comments that should the patient scream, they won't get upset. This segment predates the release of the game Dr. Mario by one year and is therefore the first instance of the brothers as doctors.
Luigi proceeds to wash his hands by soaking them in a bucket full of water, splashing water all over the place as he does so. Mario then dips a rubber glove into the water and pulls it out. As water trickles down from the glove, Luigi implies that they shouldn't waste it, so he grabs the glove and rushes it over to the tub garden, allowing the excess water to drip into it. Reaching into the bucket again, Mario pulls out Kenneth, Mrs. Periwinkle's dead goldfish, and tosses him aside. Luigi returns with Mario's glove, proceeds to put on his own pair, and asks Mario if everything is ready. Luigi asks Mario what the most important thing is, to which Mario answers with "cleanliness", only for Luigi to sneeze into his gloves, which he wipes off on Mario's scrubs.
Standing over the assembly table, Mario and Luigi use an assortment of tools to repair Inspector Gadget, who they wind up repairing in a rush job. Luigi comments that he feels like Leonardo da Vinci, but when Mario asks Inspector Gadget how he feels, Gadget, who is now just a mess of body parts, is unable to answer due to his voice being all muffled by his own arm. Luigi moves the arm, only for Inspector Gadget to ask the two of them how long they've been working for the evil Dr. Claw.
Afterwards, Mario and Luigi have properly repaired Inspector Gadget using some spare parts that Luigi picked up. Mario and Luigi then hook Inspector Gadget up to a machine to give him a bench check, to which Luigi comments that his RPM is up 3000, his oil is clean, and that he'll need to return for a left foot alignment at roughly 3000 miles. Mario presents Inspector Gadget with his 30-day parts and labor warranty and tells him not to run over any nails. Inspector Gadget prepares to write a check out to Mario and Luigi, only to ask where Luigi got the spare parts, and Luigi answers that he got the parts at a novelty store. When Inspector Gadget stands up, his hands droop down from his arms on springs, much to his dismay. Inspector Gadget grudgingly thanks the Mario Bros. for their help and heads outside before they can do anything else.
Luigi asks Mario if he should tell Inspector Gadget about any of the other changes that they made just as Gadget steps outside. While trying out one of his gadgets, Inspector Gadget accidentally activates his rocket shoes, goes flying past the basement window shouting "WOWZERS!", and crashes. To Luigi's question, Mario answers "I don't think so". Mario and Luigi then laugh and start to giggle about Inspector Gadget's rocket shoes.
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