When Penny Lane asks William to go with her to "wherever", she asks him twice. The first time William didn't like the way he said it, so he asked her to ask him again while the cameras were still rolling. Cameron Crowe like it so much that he kept the entire sequence in the film.

Stillwater was also the name of a real band that was active from 1973 to 1982. Ironically, they reunited and began touring again shortly before the film began production.

The role of Penny Lane was offered to Sarah Polley, who turned it down.

Phillip Seymour Hoffman had the flu the whole time he was filming his scenes.

This is the first Cameron Crowe movie not to feature a cameo by Eric Stoltz. Stoltz was supposed to appear on a theater marquee that said "The Crazy World of Eric Stoltz" but that didn't work out due to budgeting. Although, while the theatrical version doesn't feature Stoltz, Crowe stated in the "Untitled" DVD commentary that the Untitled version does include a reference of some sort to Stoltz, thus keeping the streak alive. Crowe encourages fans to try and find the reference in the film.

Peter Frampton makes a cameo as Reg, the road manager of Humble Pie. Frampton was that band's guitarist before he launched his solo career.