At one point during the band's performance of "Earache My Eye", the brass section can be seen not playing their instruments when they can be heard on the audio track, but in the next shot they are clearly playing along with the track.
During the "rocking van" scene outside the Roxy, the close-up shots show the van rocking from side to side, while a shot in between them from further away shows it rocking from front to back.
After Cheech picks up Chong at the beginning, Cheech's ring disappears and reappears and Tommy Chong's bandana shifts position on his head between shots.
At the beginning, when Cheech picks up Chong, the driver's side window appears and disappears between cuts.
When Cheech cuts across the road to pick up Chong, the two girls are seated on the bench waiting for their ride. When Cheech stops to let Chong in, the girls are already quickly loading their surfboards into a van that wasn't there when Cheech stopped.
Cheech feels the effects of LSD after only around 2 minutes, whereas it actually takes around 30 to 40 minutes for LSD to kick in.
However, as a comedy movie that needs jokes to pay off quickly, such instances shouldn't be taken too literally.
However, as a comedy movie that needs jokes to pay off quickly, such instances shouldn't be taken too literally.
When Cheech and Chong are crossing the street in Mexico, someone in a passing bus flashes a peace sign at the camera.
Strawberry makes a hard right turn in the motorcycle/sidecar but does not move the handlebars showing the scene was filmed on a trailer.
When the drug van is being towed from the Roxy, the fuel tank is leaking well before the tank hits the curb. The curb then "causes" the leak in the film.
After getting pulled over by the stoned motorcycle cop, the scenes repeatedly switch back and forth between Chong in the driver's seat to Cheech in the back of the truck with the girls where there is only a curtain separating them. But from the back, the view beyond the curtain should be that of bright daylight but is instead total darkness indicating the back of the truck is a set.
Around the 69'30m mark, a man with blonde hair on the left hand side of the screen momentarily glances directly into the camera.
When Cheech and Chong are waiting for the boss at the upholstery factory in Mexico, you hear Cheech rub his stomach and say, "those burritos, man," but his mouth doesn't move.
There is a person in blue shorts and a T-shirt in the rear view mirror of their car who is not in the outside shot when the motorcycle cop walks up to their car.
When Cheech and Chong enter Strawberry's house and encounter the talking parrot, a crew/camera person can be seen on the left holding up a boom mic.
When the guys are crossing the border in the van it is clearly not the Tijuana/San Diego crossing.
When Cheech is teaching Chong Spanish words, as a prank he tells him "Pendejo" means "My good friend". Chong mispronounces it "bendecko" and Cheech doesn't correct him, in fact he even says, "close enough". When the van crashes into the Mexican family's house, Cheech's prank backfires when Chong says, "hey pendejos!" he pronounces the word correctly.