In the scene where Charlie and Irene are pushing the car off the cliff, Jim Carrey says "On nine" and counts to nine very fast. This was ad-libbed and for a moment 'Reneé Zellweger' looks obviously surprised.
In the scene where the boys were doing their schoolwork, one of them expresses his dismay at the fact that Pluto was classified as a planet. Sure enough, in 2006, scientists confirmed that Pluto is not actually a planet.
The scene where Renée Zellweger kicks Jim Carrey over the railing and down the hill was done by Jim Carrey himself (instead of a stunt double) after many pleadings. He did a few takes but they used the first one. A mattress was used for him to pop back into frame.
At one scene in the motel, a smashed watermelon is visible by the bed with no explanation as to why or how it got there. This is because the scene involving the watermelon gag was cut, but the smashed watermelon is still in the shot. The gag was going to be that he was having sex with the watermelon. But shortly before its release, American Pie came out and it no longer seemed appropriate due to using the same joke.
Michael Bowman got the role by answering an ad from acting lessons. He has since "somewhat regretted" taking the role due to the on-screen discrimination his character gets. Like his character Whitey, Bowman is an Albino himself.
In the scene when Charlie kisses Irene, he says to her "my ass is sore" the song thats playing is "Deep Inside Of You" by Third Eye Blind. Coincidently, the lyrics you can hear after Charlie says this, clearly say "it goes deep inside of you" which is a pretty good explanation for why Charlie has a sore ass.
When Peter Farrelly chose the group, 'Hootie & The Blowfish' to re-record the Orpheus classic "Can't Find The Time", the sheet music that was provided by the song's publisher contained errors in the lyrics. Hootie recorded the song mistakes and all - and it was not until the band invited the songwriter on stage during a show that they learned they had been singing the wrong lyrics.
In the film, Charley has three full-grown Black children. This is an obvious reference to a skit done by the late 'Andy Kaufman' on Late Night with David Letterman, where Andy brought out three full-grown Black men as his "adopted" sons. Jim Carrey portrayed Kaufman in the 1999 biopic Man on the Moon (1999).
In the scene where Hank is enraged by the softball player carelessly littering, all of the softball players' shirts say Cerrone. This is a reference to the writer who assisted the Farrelly brothers, Mike Cerrone.
There are several moments throughout the film that Hank whistles along with the soundtrack, but Charley never does. This could either be a simple fourth wall break, or it could be implying that Hank is somehow aware of the music.
Director Peter Farrelly was and is a huge fan of the band, Orpheus, whose 1968 hit single "Can't Find The Time" is covered by 'Hootie & The Blowfish' for the movie's soundtrack. According to an interview which appeared in the Milford Daily News, while in college, Farrelly even dated an Orpheus member's ex-wife who was the inspiration for Amy Smart's character in the film, Outside Providence (1999).