No one expected Back to School to be a hit. But the Rodney Dangerfield comedy—which saw the legendary comedian starring as Thornton Melon, a self-made millionaire who attends Grand Lakes University with his son, Jason, and becomes the most popular man on campus—ended up becoming the second highest-grossing comedy of 1986 (only Crocodile Dundee made more). To celebrate its 30th anniversary, here are some facts about the only film that ever dared to pair Dangerfield with Robert Downey Jr., Sam Kinison, and Kurt Vonnegut.

1. HAROLD RAMIS MADE A KEY REWRITE.

In the original draft of the script, Thornton still tries to motivate Jason by attending his college, but he was a "poor schmo." It was Harold Ramis who suggested it would be a funnier movie if Thornton were rich. Dangerfield convinced Orion Pictures to delay production and hire Ramis to rewrite the script.

2. JIM CARREY WAS CONSIDERED FOR SAM KINISON'S ROLE.

Jim Carrey was eventually deemed too young to play Professor Terguson. Years later, producer Chuck Russell remembered Carrey when he was tasked with directing The Mask (1994).

3. IT WAS THE FIRST TIME WILLIAM ZABKA REALIZED HE MIGHT BE GETTING TYPECAST AS A VILLAIN.

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When William Zabka—who played Johnny Lawrence in The Karate Kid and Greg Tolan in Just One of the Guys—landed the part of Chas in Back to School, he started to notice a pattern forming. "When Back To School came around, that was the first time I thought, 'Hey, wait a minute. This is starting to happen too much,'" he said.

4. ROBERT DOWNEY JR. WAS SHOOTING SATURDAY NIGHT LIVE AT THE SAME TIME.

The then 20-year-old actor burned the candle at both ends then. He told Rolling Stone, "I'd fly back to Los Angeles for a couple of days during the week to shoot the movie and then fly back and, 'Live, From New York, It's a Tired Young Man!'"

5. SALLY KELLERMAN ONLY KNEW RODNEY DANGERFIELD FROM HIS BEER COMMERCIALS.

Sally Kellerman admitted to Orange Coast Magazine in November 1986 that she "didn't really know who Rodney Dangerfield was," only having seen him in his Miller Lite commercials. Therefore she "wasn't just flipped out of my mind at being the woman who lifts him up. I thought, 'Oh, whoopee! You're going to get to play his love interest.' Ye gods, I knew I'd made it." But the two got along. "The second day we met, he said, 'Did you change your hair?' And I said, 'No, did you?' After that I liked him so much. He's such an odd guy."

6. GRAND LAKES UNIVERSITY WAS REALLY THREE DIFFERENT COLLEGES.

The University of Wisconsin-Madison, University of Southern California, and California State University, Los Angeles teamed up to portray the fictional Grand Lakes University. The one college Dangerfield applied to for his higher education was the University of Wisconsin. He said, “It took 40 years, but I finally got here.”

7. THE MOVIE'S LOCATIONS PROBABLY LOOK FAMILIAR.

The big oral exam was in the Nimitz Room of Bob Hope Patriotic Hall, where Jennifer Beals (well, her body double) danced in the final scene of Flashdance (1983). Dr. Diane Turner's residence is the same home where Jamie Lee Curtis gets terrorized by Michael Myers in Halloween (1978).

8. ZABKA TRIED TO MAKE CHAS FUNNIER AND LESS OF A BULLY.

"I actually tried to have more fun with Chas, because I thought, 'I’m going to be funny now. I really don’t want to just play a jerk,'" Zabka explained to The A.V. Club. "So I actually put on a funny walk and I had a scarf a bunch of times. I made him way more funny than he actually turned out in the film. They cut out most of my funny. In fact, the director [Alan Metter] pulled me aside one day and said, 'We need you to be more like the guy you did in The Karate Kid. You’re coming off too likable and funny.'"

9. ZABKA AND DOWNEY JR. MADE MUSIC TOGETHER.

Chas and Derek Lutz hung out in Downey's hotel room, where Downey would play his keyboard and Zabka would play his guitar. The two also watched movies and tried to figure why Christopher Walken was "so genius."

10. RODNEY WAS IN HIS ROBE A LOT.

Zabka and Dangerfield first met early one morning in a Madison, Wisconsin hotel elevator. Dangerfield wore a blue robe with his hair sticking up. After Zabka introduced himself he asked Dangerfield why he was in a robe. “I gotta get in the sauna," Dangerfield replied. "I gotta get the pot out of my lungs.” [Laughs.] “You, you’re young. You can handle it, but me I gotta get it out.”

Kellerman got the impression that the star of the movie was a "very serious guy on set." She noted that he wrote notes in his script every night, sitting in his robe.

11. THE DIVERS WERE EXPERT COLLEGE DIVERS.

Director Alan Metter asked the divers to "do their worst" to play the Grand Lakes diving team.

12. DANNY ELFMAN WAS THE COMPOSER.

Danny Elfman and his band, Oingo Boingo, were in the movie playing "Dead Man's Party." "It was just a quick thing. I can’t even remember if it was one or two days," Elfman tried to recall. "It was funny because Robert Downey Jr. was sitting there at a mock mixing board to mix the band and we were essentially lip synching the tune."

13. IT WAS DEDICATED TO ESTELLE ENDLER.

The "For ESTELLE Thanks For So Much" message that appears before the end credits was dedicated to Rodney's manager, and Back to School's executive producer, Estelle Endler, who died during filming.

14. EVERYONE SHOULD HAVE PAID MORE ATTENTION IN LAW CLASS, BECAUSE THERE WERE A LOT OF LAWSUITS.

A husband-and-wife screenwriting team claimed they wrote the basic plot of the movie in their screenplay Second Season, which they submitted to Orion Pictures in 1979. Alan Metter sued Orion for not paying him all he said he was due. Dangerfield later counter-sued for suing without reasonable cause. Casting director Caro Jones sued the producers of Back to School and said she did not receive full pay or the proper screen credit.

15. RODNEY MIGHT NEVER HAVE GOTTEN RESPECT, BUT KURT VONNEGUT DID.

In 2002, Kurt Vonnegut told Indianapolis Monthly that he was a fan of the film, and remembered all of the lines about him. "'Hey, Vonnegut, can you read lips? F**k you!' I loved it. And it earned me more respect from my druggist and my dry cleaner here in New York than anything I’d ever done."