From the Super Mario Wiki
David Horowitz (June 30, 1937 – February 14, 2019) is a famous news reporter and consumer advocate (not to be confused with the conservative activist of the same name) who has also made an appearance in The Super Mario Bros. Super Show!
In The Super Mario Bros. Super Show! live-action segment "The Marios Fight Back", David Horowitz appears at Mario Brothers Plumbing to interview Mario and Luigi, who claim to have created a clog clearing product that could get rid of clogs in three minutes or less.
At Mario and Luigi's apartment, after telling his viewers about Mario and Luigi Mario Brothers Clog Cleaner product, Horowitz instructs Mario and Luigi to test their product on a nearby sink. After telling Mario and Luigi to unclog a sink, he watches as Mario works on it while Luigi gives him tools, which Mario throws away quite haphazardly.
After some work on the sink, Mario instructs Luigi to give him some Mario Brothers Clog Cleaner while he asks Horowitz if he is on nationwide television; answering Mario's question, Horowitz tells him that no, he is on worldwide television. After answering Mario's question, he notices that Mario is putting an awfully large amount of Mario Brothers Clog Cleaner in the clogged sink, but is reassured by Mario and Luigi not to worry at all, saying they are professional plumbers.
Eventually, Horowitz is accidentally knocked unconscious by Mario who, while cleaning his hands, carelessly throws a can of Mario Brothers Clog Cleaner behind his back, which hits Horowitz on the head.
As he lays unconscious, slumped against the clogged sink, which is shaking violently, Mario and Luigi, seeing that almost three minutes have passed and the sink is still clogged, decide to try an unclog it using some Mario Brothers Plant Food; after pouring Mario Brothers Plant Food in the sink, leave their apartment for some pizza.
Eventually waking, Horowitz, regaining his bearings, notices something in the clogged sink. Upon closer inspection, he finds a horrific monster has been mutated from the clog in the sink. After almost having his arm gnawed off by the clog creature, Horowitz, in a panic, leaves Mario Brothers Plumbing quickly, not waiting for Mario or Luigi to return.