At the top of "Simpsons" fans' lists of their favorite episodes is usually the season 4 classic "Marge vs. the Monorail." Written by Conan O'Brien, the episode is "The Simpsons" at perhaps its sharpest and most energetic. There are a million jokes per minute here, all of them hits. And even if you don't find them all funny, at least you can enjoy the catchy musical number the show uses to introduce Lyle Lanley, the smooth-talking salesman who tricks the town into spending all their money on a monorail that doesn't work.

It's not a full-on parody or anything, but the song Lanley sings is inspired by "Ya Got Trouble," from the 1962 film "The Music Man," a sequence where a con-man (played by Robert Preston) stirs up a moral panic and uses it to convince the townsfolk to let him start a marching band. Just like Lyle, the guy plans to skip town the moment he gets the money.

In an interview with The Ringer, O'Brien explained how that song was a bit of an obsession for him in his early years. "I always wanted to play the Robert Preston part and do the 'Trouble' song," he said. Although the singing role in the episode ended up going to Phil Hartman, Conan at least got to write the Monorail song, and he had zero interest in disguising just how much it was inspired by "The Music Man."

"I just love the 'Trouble' song," O'Brien admitted. "We knew that it had to have that kind of feel." O'Brien's chance to sing the Monorail song himself would come years later at The Hollywood Bowl, and his love for the tune still seemed as strong as ever.

Hardly The Show's Only Musical Number

"The Simpsons" is famous for its musical numbers, with hits like "Who Needs the Kwik-E-Mart?" and "Dr. Zaius" getting stuck in viewers' heads for weeks after the related episodes aired. Even in later seasons, the musical numbers are still dependable winners; season 15 might not be anyone's favorite season of the show, but the various "Evita" parodies in "The President Wore Pearls" are some of the best things "The Simpsons" has ever done.

It's not the only animated sitcom out there with surprisingly impressive musical chops. The minds behind "Family Guy" clearly love musicals and they like to throw parodies of them into the show all the time. And because "Family Guy" is far less concerned with plot, their musical sequences get to be far more self-indulgent. In season 5's "Road to Rupert," the show features a two-and-a-half minute scene where it basically just recreates "The Worry Song" from the 1945 kids' film "Anchor's Way," except Gene Kelly is dancing with Stewie instead of Jerry Mouse. It has nothing to do with the plot, but that's part of the appeal.

"South Park" creators Trey Parker and Matt Stone are also major musical fans; not only did they go on to write an actual Broadway hit with "The Book of Mormon," but 1999's "South Park: Bigger, Longer & Uncut" is filled with songs that are genuine bangers. Even 20+ seasons into the show, they are still capable of casually throwing catchy, thematically appropriate songs into episodes, even with the show's famously hectic production schedule.

At this point, it almost seems like a rule that if you want your cartoon sitcom to last for 20+ years, you better have some good taste in showtunes.

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