Continuity mistake: In the scene where William is sitting in the tub working on his notes, after Penny comes in and sits on the toilet, he scrambles out of the tub and most of the notes which were on the side of the tub fall on the floor. In the next cut when the camera is positioned near the bathroom door, looking in, all of the notes are back on the side of the tub and none are on the floor.
Continuity mistake: Backstage at the first concert, William is sitting alone writing when Penny comes to talk to him. She has her glasses in her hand as she frames his face to guess his age. As the scene is shown from different angles, she is shown both with the glasses in her hand and without them in her hand depending on the shot.
Continuity mistake: In the scene where Russell jumps off the roof into the pool, you can see that two people from the top left corner jump into the water to save him; then in the next shot you can see that no one has jumped in because the surface of the water is undisturbed and then the same people jump in again.
Continuity mistake: In the poker scene where Russell loses and has to trade Penny for a case of Heineken, Russell gets up to talk to William. Russell brushes his hair behind his ears, and in the next shot, his hair is down again. His hair goes back and forth the entire scene.
Continuity mistake: During the scene when the entire group are singing 'Tiny Dancer' on the bus, William cuts Penny off just as she opens her mouth to sing the next line, however the audio of everybody else singing doesn't start that line for another 3-4 beats after Penny opened her mouth.
Continuity mistake: In the scene where Russell and Jeff are arguing about the band's T-shirt their manager is standing behind Jeff, but when Jeff says that Russell " allowed Dick to manage us" Dick is sitting on the couch. At the end of the fight, the manager is standing behind Jeff again.
Continuity mistake: In the scene where Penny overdoses, she's wearing calf-high tan boots. She falls over on the couch and dances with William while wearing them. When the doctor rushes in and forces her to vomit in the tub, however, her boots are suddenly gone.
Continuity mistake: In the scene when Penny is completely out of it because of her overdose, she and William are dancing. At one point William's left hand touches her face. We see he is wearing a white dotted shirt that comes down to his wrist. When the shot zooms back out, he is wearing a jacket over that shirt and the sleeves are rolled up to his elbows.
Continuity mistake: Right after the scene in which the band has a fight over the T shirts, which Dick says is the band's first T shirt, you see Russell and William go to a house party in Topeka. One of the attendants of the party has a Stillwater shirt that is of a different design than the shirt first revealed at the show only minutes prior, which again was supposedly their first shirt. The shirt seen on the partygoer can also be seen later in the movie.
Continuity mistake: In the scene toward the end of the movie where William and Anita go home, Elaine comes to meet them on the porch. Will goes inside while Elaine and Anita hug. In the first shot they are hugging cheek to cheek (both faces toward the camera), but the next shot shows them breaking their hug and they are hugging with each chin on the other's shoulder.
Continuity mistake: When William is 11 his eye colour is dark brown. When he is 15 his eye colour blue-green. You would think the makers would have tried to make the two William characters have the same characteristics.
Continuity mistake: In the scene where Penny and William are at the airport and shes ready to go back home after her overdose, her hair is a complete mess, it looks frizzy and dirty. However when she is shown on the plane a few minutes later, her hair is back to normal, curly and clean, like she just did it.
Continuity mistake: While the band are talking about what William wrote about them in Rolling Stone and Russell is lying on the bench, the bag on his head has a white label which appears and disappears between shots.
Continuity mistake: In the radio station scene, when Lester Bangs is pulling albums from the shelves and tossing them on the floor, he pulls Yes' Fragile and tosses it. In the very next shot, it's back on the shelf. Two shots later, it's back on the floor - or some other time-warped dimension, but not on the shelf.
Sapphire: William? I forgot to tell you. Your mom called. She says you gotta call home immediately. And she says to tell you, "I know what's going on."
Trivia: Penny Lane picks up William to go see Stillwater at the Riot Club in L.A. In the very beginning of the scene in her car, a reflection passes up the windshield over William's face as they are driving. The Reflection is the prism and spectrum from Pink Floyd's "Dark Side of the Moon" album. There are no other reflections in this scene.