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." The crew found this so hilarious, they ended up using it as a post credits scene.
Although his character is supposed to be 94 years old in this movie, Burgess Meredith was in fact 85 years old when this movie was filmed and is only 17 years older than Jack Lemmon who portrays his son in this movie.
The address of 11291 Chloe Ln. Wabasha, MN 55981 which appears on Grandpa Gustafson's shanty door is actually the address of Slippery's Bar & Grill in Wabasha, MN which is the bar referenced in the film.
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.
Grandpa Gustafson's address is written on his shanty door when he is out ice fishing. It is visible only for a split second after he takes the paper bag of beer from his son. It is listed as: J.W. Gustafson 11291 Chloe Ln. Wabasha, MN 55981
Although the door to his ice shanty says the initials of his first and middle name are JW, Burgess Meredith's character of Grandpa Gustafson in this movie, and its sequel Grumpier Old Men (1995), is never actually addressed by his real first name by any of the characters.