The stunt where Jim Carrey (Charlie) throws himself out of the car was done in only one take.
The glasses that Michael Bowman (Casper AKA "Whitey") wears are his real-life glasses, including the little microscope on the end.
During the "Hank Breastfeeding on the MILF" scene, Jim Carrey unknowingly latched onto Shannon Whirry's right-nipple; Carrey thought Whirry was wearing a mammary-prop at first, until he tasted it and quickly found out that they are genuinely her lactating ample breasts. Carrey explains: "It's very rare that I get to a place where I am actually kind of humiliated, but that was one of them. It was so embarrassing to me, I was like embarrassed for the girl, but she was fine with it. She was like 'Yeah, whatever.' But I was literally apologizing to her between every take. When it was time to film it, I had to empty the studio. I couldn't do it in front of anybody." This is surprisingly ironic, because Carrey at other times would openly admit his love for big-breasted women; while Whirry has no qualms about doing topless scenes and "wet-nursing stunts", because ever since 1992 which was the next year after the film's script was completed, she had performed in over a dozen erotic films in her acting career.
Jim Carrey ad-libbed the moment when he asks his sons to kiss him before he leaves. One of them looks obviously surprised.
The scene where Renée Zellweger high-kicks Jim Carrey over the railing and down the hill was done by Jim Carrey (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.