The Woman Now clinic has a single glass front door from the outside, but inside it is a much wider double door.
The mailbox in front of Bleeker's house in which Juno and Leah put the Tic Tacs, is missing from the final shot where Juno and Bleeker are playing guitars while sitting on the steps.
When Juno goes to see Paulie at night and mentions how hard he's studying, when the camera changes angles there is nothing on the paper when he was clearly writing when she entered the room.
When Juno enters the drug store for a pregnancy test a guy and girl are shown outside the window. The guy was sitting on a statue and talking to the girl. When Juno goes inside the store, the window is shown again from the inside but the girl, guy and statue have disappeared.
When Juno spots Mark's Les Paul it appears a dark red/brown model but when she subsequently enters the room and picks it up it's a gold-top model.
In the ending credits the song "Doll Parts" is credited to Courtney Love, omitting its co-writer, Hole guitarist Eric Erlandson.
No high school in a northern state would have track practice in winter time.
Juno is seen wearing her street clothes when she gets an ultrasound. Pregnant women who get an ultrasound. They are required to remove their street clothes and wear a hospital gown during the ultrasound procedure.
Several vehicles are shown without front license plates, even though they are required in Minnesota.
When Bleeker is talking to Juno in the hallway at school while
holding a box of donut holes, the box changes positions in his hands every time the angle changes. In his DVD commentary, director Jason Reitman explains that this was an intentional cheat (one that irked his script supervisor!) to keep the donut holes visible through the box in both camera angles.
When Juno goes to visit Mark and Vanessa to give them the ultrasound photo, Mark tells Juno that Vanessa is working late to accumulate time-off for when the baby comes. As there is snow on the ground, it is clearly winter. However, when Vanessa comes home, it is still light outside. Minnesota in the winter is dark around 4pm.
The movie is, in fact, filmed entirely in Canada as shown in Filming Locations. Furthermore, in Trivia it's explained they made changes to the scenery, fake snowstorm, in order to have the seasons mirror the pregnancy's trimesters.
In the Mall scene when Venessa first feels the baby kick, she tells Juno " I felt him" but the gender hadn't been revealed yet.
He is used to refer to a person with an unknown sex ie they. Also, it could be a foreshadow of it being a boy.
The pregnancy test Juno uses has no inner wrapping nor any directions in the box, just the test itself.
Mark tells Juno that the "Most Fruitful Yuki" comic he shows her came from Japan, but it appears to be the size and format of a Western comic book. Japanese comic series are published in bound volumes that are smaller (commonly 5x7 inches, as opposed to the usual 7x10 of American comics) and several hundred pages long.
The small quartz decorator clock in the kitchen of Juno's house, visible over Mac's right shoulder in several scenes, has a large, red sweep-second hand that reveals that the clock is obviously not running, presumably to preserve continuity and avoid having to reset the hands for every retake.
At the end of the movie, the words 'SUMMER' are superimposed over the scenes which clearly show many many spring blossoms on the trees.
Mark would not have danced to "All The Young Dudes" at his 1988 high school prom. This song came out in the early 1970's. And there was no new cover of it in 1988.
When Juno encounters Vanessa outside in an elevator the mall scene, Juno states Vanessa's name in surprise but she mouths Jennifer (the actress' name rather than the character's name). The 'J' can still be heard.
The CD of 'Mott the Hoople' that Juno brings to play for Mark actually doesn't have the song "All the Young Dudes" on it, which she proceeds to play.
When Juno is laying on her front windscreen at night, the reflection of the camera is visible in the window as it pans down to her in shot.
In Mark and Vanessa's PennySaver ad, the area code is listed as 320 for St. Cloud, MN. But every other ad lists the 310 area code, which is an area code in Los Angeles, CA.
The bottle of Sunny D Juno is drinking in the opening is the type of bottle found in Canada with a rectangular shape rather than the circular shaped bottles found in the US, and the size is marked on the bottle in liters instead of ounces like the US bottles.
When Juno and Leah are at the mall, two uniquely Canadian chain kiosks, People's Jewelers and Rogers Communications, can be seen in what is supposed to be a mall in Minnesota.
When Juno pulls the van off the highway, mountains can be seen in the background of the long shot. There are no substantial mountain ranges in the Minneapolis/St. Paul area, where the movie is supposedly set.
Near the end when Juno is in the car, stopped by the side of the road, you see a range of mountains in the distance. Minnesota has no mountain ranges like that. The scene was obviously shot in British Columbia, Canada.
Juno explains that her name comes from the wife of the Greek god Zeus. In fact, the Greek team were Zeus & Hera, the Roman team were Jupiter & Juno.
When Juno is talking to Leah on the phone, she sarcastically says she is Morgan Freeman and asks if Leah has any bones that need collecting. Morgan Freeman wasn't in The Bone Collector (1999).
When Juno enters labor, she shouts "Thundercats are go!", an error or more likely a mixed reference to both the American cartoon series "Thundercats (1985) ho!" and the British Supermarionation series "Thunderbirds (1965) are go!".
During the chromatography scene, the formula to work out the RF value is correct but an incorrect answer is given with 2 shown instead of 0.5.
In one scene when the track team is running on the track they're running the wrong way.