From the Super Mario Wiki
In The Super Mario Bros. Super Show! live-action segment "Plumbers of the Year", the Imperial Poobah appears at the apartment of Mario and Luigi, looking for Mario and Luigi. Shocked that the Imperial Poobah is at their home, Mario and Luigi, after reciting an oath and bowing, are told by the Imperial Poobah to rise. After doing as the Imperial Poobah instructs, Mario and Luigi ask the Imperial Poobah what he is doing in their home, only for Mario and Luigi to get the response from the Imperial Poobah that he is there to honor Mario and Luigi with the title of Plumbers of the Year.
After announcing this, the Imperial Poobah proceeds to tell Mario and Luigi that before he can give them the Plumbers of the Year trophy, he has to conduct the Imperial Investigation, a routine check to see if Mario and Luigi are worthy to become Plumbers of the Year. After stating this, the Imperial Poobah go on to say that Mario and Luigi have nothing to worry about if they are truly worthy of being Plumbers of the Year and goes on to continue saying "Nothing to worry about" over and over again, as if in a trance. As the Imperial Poobah continues to say the same words over and over again, Luigi begins to slap him on the cheek, trying to get the Imperial Poobah back to normal.
Later, after inspecting the plumbing of Mario Brothers Plumbing, the Imperial Poobah congratulates Mario and Luigi on having perfectly flawless plumbing; directly after the Imperial Poobah says this though, a nearby pipe begins to leak water and steam. As water and steam flows from this pipe, the Imperial Poobah says that this changed everything, crumples Mario and Luigi's inspection paper and tells them that maybe they did not have what it takes to become Plumbers of the Year. Luigi, frantic, begins trying to convince the Imperial Poobah that the leaking pipe can easily be fixed.
After, as Luigi tries to fix the leaking pipe, the Imperial Poobah watches him, stating that there is no way that the pipe can be fixed. Despite the Imperial Poobah's objections, Luigi continues to try to fix the leaking pipe and proceeds to tell Mario to get him some leftover pizza for him. As the Imperial Poobah looks onward, Mario grabs an extra-cheese from a fridge and gives it to Luigi, who uses the cheese on the pizza to fix the leaking pipe, which, surprisingly, fixes the pipe.
Amazed at Mario and Luigi's inventiveness in plumbing, the Imperial Poobah decides to crown them as the Plumbers of the Year and after a lengthy speech, officially gives Mario and Luigi the title of Plumbers of the Year and also tells Mario and Luigi that they will receive some steak knifes, a pair of dice and hand choppers in the mail in six to eight weeks. After thanking the Imperial Poobah for giving them the title of Plumbers of the Year though, Mario, Luigi and the Imperial Poobah can only watch as several nearby pipes burst, unleashing water and steam.
As Mario and Luigi attempt to repair these leaking pipes, the Imperial Poobah, deciding to help Mario and Luigi with their predicament, grabs a nearby telephone and tells whoever is on the other end of it to send over several pizzas with extra cheese on them.