Before the lights come up at Stillwater's Cleveland show, fans are waving Chem-Lite glow sticks. Glow sticks were first patented in October 1973, and weren't widely available for several years after that.
When William calls the desk to report Penny's 'accident' with some Quaaludes, a close-up shows the Quaalude Bottle. The label should say Rorer (Pharmaceuticals), not 'Lemmon'. The Lemmon Company didn't make Quaaludes until 1978.
In the final concert, as the band walks onto the stage, several modern intelligent lights (MAC600s) are visible. The lights were first released in 1997. In other scenes, the instruments lighting the band are halogen and metal
halide lamps, which also didn't exist in the 1970s.
In the Untitled version, when William and Lester Bangs are alone on the San Diego corner, just after Lester refers to "his many fans", a 1990s Obey Giant (aka "Andre Has a Posse") poster is on the traffic box on the left.
After William says goodbye to his Mom and goes to meet Penny Lane for their trip to Los Angeles, he runs across a street. On the right side of the screen, a 1980s-style Honda sedan is parked among the myriad 'period' vehicles.
On the bus when everyone is singing "Tiny Dancer", William says something to Penny. Penny already had her mouth open to sing the next lyrics "Hold me closer." However, the next line is actually "Count the headlights on the highway."
When William is sitting in the bathtub, Penny Lane comes in to use the bathroom. Startled, William knocks his notes off the edge of the tub. In the next scene, the notes are still lined up on the edge of the tub.
When Russell is about to be interviewed in William's room, a shirt is on the chair Russell sits on. He turns the chair around and throws the shirt on the floor. In the next shot, the shirt reappears on the chair.
When Lester Bangs is interviewed at the radio station, he picks the Yes' album "Fragile" from the shelf, says "Yes? No !", and throws the record on the ground. When he then picks another record, "Live American Woman", and "Fragile" is back on the shelf.
When William Miller and Russell Hammond are walking outside
the concert, a VW bus is driving behind them and passes them on the street. In the next shot, the same VW bus is back 50 yards or so again. It then passes by again less that 10 seconds later and the driver invites Russell and William to a party.
During the backstage argument in Topeka, Jeff points to Dick sitting on a couch next to Ed. Suddenly, as the argument ends, Dick is standing behind Jeff. The preceding shots would have shown Dick getting up from the couch to break up the fight, but he is never seen in the background.
When William Miller is in the Rolling Stone's conference room with Ben Fong Torres waiting for the fact-checker to return, a black telephone is on the corner of the table, to Miller's right. When the fact-checker returns, there are several quick cuts with the phone visible in each. As she leaves, that corner of the table is clearly visible, but the phone is not. In the next cut, the phone is there again.
When William is writing in the tub and Penny Lane walks in, Post-It Notes appear to be all over the tub. Post-it Notes were invented in 1977, and not released to the public until at least 1979. In the DVD commentary for "Untitled", Cameron Crowe says the notes are folded yellow legal paper.
Throughout the movie, various albums and tracks are mentioned, heard and seen, even though they weren't released at the time the individual scenes are set. However, they are "of the period," and suit the scenes for other reasons.
When the sister leaves at the beginning, she puts on Paul Simon & Art Garfunkel's "Book Ends" album to play "America." We hear the song begin crisply, but on that album, "America" fades up as the tail end of "Save the Life of My Child" is fading out.
The goof items below may give away important plot points.
When Dick, the band's manager, fights with the owner of the venue after Russell is shocked, his cowboy hat falls off. In the next shot, he boards the bus wearing the hat. It's noticeable in the "Untitled" version, but not in the theatrical release.
Russell is electrocuted as he reaches for the microphone, as though to sing backing vocals. The song, which plays during the radio interview scene and on the "Stillwater" CD included with the Director's Cut, has no backing vocals. However many rock bands alter songs during a live show.