At the end of the theatrical trailer, there is an outtake of Walter Matthau in the bath tub saying directly into the camera "If I'd known there was going to be a nude scene, I would've asked for an extra million."
Dean Martin and Jerry Lewis were strongly considered for the roles of John and Max, respectively, but both declined because of Martin's frail health which prevented him from taking the role. Martin died in December of 1995, right around the exact same time that this movie's sequel, Grumpier Old Men (1995) was released in theaters.
John states that he was a teacher at Wabasha High for 30 years. Though Wabasha does have a high school, it combines with the town of Kellogg to create Wabasha-Kellogg High School.
When Chuck, Max, and John are talking about Ariel at the bait shop, John says that Ariel came to see him last night at 1:30 am. Ariel came to see him two nights ago, not last night.
Max Goldman: You know what Jacob said? Jacob said old Billy Hensel was killed in a car crash. Cleared his car straight off the bridge into the Mississippi.