Movie Goof (audio/visual unsynchronized): When Sonny arrives at work, as the Security Guards open the gates for him, we hear them chatting, but their mouths aren't open/are out of sync.
Movie Goof (continuity error): The ripped pieces of paper from Sonny's drawing land in front of the mural, yet they have all vanished as the muses dance in "I'm Alive."
Movie Goof (continuity error): When Sonny first sees the auditorium that eventually becomes Xanadu, the letters on the roof of the building that spell out auditorium are missing the A and R. Later when Kira takes him to the auditorium, the T is now missing. The following scene when Sonny and Danny arrive at the auditorium, the T is back. Finally, when Sonny and Kira are slow dancing in front of the auditorium before it magically transforms into the finished Xanadu exterior, the T is missing again.
Movie Goof (continuity error): Sonny is left-handed, as we see when he is painting, yet on a close-up shot where he is drawing, it's a right hand holding the mechanical pencil.
Movie Goof (audio/visual unsynchronized): The tap dancing sounds during "Whenever You're Away From Me" are out of sync with their visual tapping.
Movie Goof (continuity error): While pouring champagne at the end of a week of building Xanadu, Danny pours into Sonny's glass then goes to pour into his, when the camera switches mid sentence, Danny is filling Sonny's glass again.
Movie Goof (crew or equipment visible): Near the end of "Dancin'", when the two 80's dancers meet the two 40's dancers, there is a white scrim behind them. If you look at the bottom of it, you can see several pairs of white sneakers and blue jean-clad legs behind it (the stagehands that move the 80's and 40's set together).
Movie Goof (crew or equipment visible): Camera crew reflected in the big mirror on the ballroom dance scene.
Movie Goof (continuity error): Richie's large painting stands in front of the stairs as Sonny enters. When Sonny leaves, the painting is now beside the stairs.
Movie Goof (audio/visual unsynchronized): When Sonny discovers Kira skating on the floor of the Xanadu building, he calls "You!" from the balcony above. Kira's repartee is "Me," which she says as her face is set towards the ground. Immediately after, she looks up at Sonny and can be seen silently mouthing the same line.
Movie Goof (audio/visual unsynchronized): When Danny and Sonny come to the auditorium, there is a flashback scene where three female singers take the stage in the 1940's sequence. They are all mouthing the words but it is Oliva Newton John doing the singing throughout. The dark haired one also forgets to move her lips occasionally.
Movie Goof (continuity error): In the scene at the art studio when Kira sneaks up on Sonny painting, the color of his painting smock changes back and forth between medium and light blue.
Movie Goof (continuity error): In the final dance sequence in the Xanadu Club, the second muse to appear in "I'm Alive" has wavy hair just above her shoulders. In the last shot, her hair is straight and almost down to her waist.
Movie Goof (continuity error): When Sonny borrows the moped to follow Kira, the weather is warm and the sky is clear. A few moments later on the pier, the weather has become misty and the sky overcast.
Movie Goof (audio/visual unsynchronized): The keyboard player in the "Dancin'" segment.
Movie Goof (continuity error): In the beginning we see Sonny sketching a large pastel drawing. He then rips it up into pieces and throws it out the window. As we watch the pieces float, they are all blank and white, with no drawing on them.
Movie Goof (factual errors): The sun can't rise out of the Pacific ocean when viewed from Continental America.
Movie Goof (audio/visual unsynchronized): The rock drummer is out of sync with the drum sounds during the rock and roll big band scene.
Movie Goof (continuity error): At the end of "I'm Alive" when Kira bumps into Sonny, the branches behind Sonny go from still, to blowing in the wind, instantly.
Movie Goof (continuity error): When Sonny enters Airflo records, he goes over to hang his coat up. He then begins to push an easel across the room, which was not beside the coat rack in the previous shot.
Movie Goof (crew or equipment visible): In the art studio Richie is working on a painting and it only has a small part finished. In the next shot the painting is completely finished.
Movie Goof (continuity error): At the start of "Don't Walk Away" the rose blooms with nothing around it. In the next shot leaves and stems are right beside it.
Movie Goof (continuity error): When Sonny talks to Kira in her dimension, Kira alternates from standing on or off the glowing yellow lines.
Movie Goof (continuity error): When Sonny first visits the painter's workshop, Richie is working on a painting, which is only partly done. When Richie turns to greet Sonny, the painting is almost competed.
Movie Goof (plot holes): How was Danny able to catch up to Sonny at the pier, if he was on foot and Sonny was on a moped? And also, how did Danny know where he was going?
Movie Goof (continuity error): In "Whenever You're Away From Me" Kira and Danny begin to dance in front of a large wall mirror, yet in the next shot it has completely vanished, and they are just dancing in front of a plain white wall.
Movie Goof (continuity error): The second muse to appear in "I'm Alive" has wavy hair just above her shoulders. In the final dance sequence of "Xanadu" in the Xanadu Club as they transform back to muses, in the last shot, her hair is straight and almost down to her waist.
Movie Goof (continuity error): At the beginning of the movie, the muses in the painting on the mural are detailed and fully rendered. Later, when Sonny is about to jump into the mural, the muses in the painting are sketchy and lacking detail.
Movie Goof (continuity error): Several times in the art studio scenes, Sonny's paint pallet is replaced with few paintbrushes and vice versa.
Movie Goof (continuity error): The position of the roller skates hanging around Sonny's shoulders changes when he first enters the auditorium.
Movie Goof (continuity error): In "The Fall", When Danny is skating in Venice Beach, his red fish shirt is buttoned. In the next shot, his shirt is unbuttoned.
Movie Goof (continuity error): The jacket, paintbrush, and palette held by Michael Beck when visited by Kira.
Movie Goof (miscellaneous): In the scene where Danny and Sonny meet, note the clothing that everyone's wearing. Everyone around them is dressed in warm weather clothing, like bikinis and short shorts, yet Danny and Sonny are both wearing long-sleeved coats, cold-weather pants, and - in Danny's case - a wool scarf and a hat.
Movie Goof (continuity error): The sign on the doors of the old auditorium changes briefly between shots.
Movie Goof (crew or equipment visible): In "Whenever You're Away From Me", Kira and Danny dance by a mirror, where you can see the cameraman.
Movie Goof (continuity error): At no time during the scene where Sonny falls into the water, is pulled out, and has coffee with Danny in the diner do we see Sonny carrying or wearing roller skates. Yet he goes from the diner to hitch a ride on a van, and he's wearing roller skates. Where did they come from?
Movie Goof (continuity error): In "The Fall" musical sequence, Sonny is shown roller skating alone along a beach-side boardwalk. In the opening shot heat waves shimmer up from the ground, and passersby are dressed in bathing suits and other warm weather clothing. Further inserts of Sonny skating show the sky being gray and the people in the background are dressed in heavy winter coats.