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.
The sixth pairing out of ten movies of comic actors and great friends Jack Lemmon and Walter Matthau.
After filming this movie in Minnesota in freezing temperatures, Walter Matthau was hospitalized with double pneumonia.
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.
Jack Lemmon and Walter Matthau did not think that this movie would be anything special, and were surprised that it became a box office success. On a budget of around $35 million, it made $70 million.