Old James (even though he is not supposed to actually exist) is one of the extras in the background the first time in the jail cafeteria.
During the first scene where Thurgood has sex with Mary Jane while it shows different pictures of them in various positions Thurgood is seen wearing at least 2 different pairs of boxer shorts.
The noodle disappears from Thurgood's mouth when "The Guy On The Couch" throws him the note saying that Kenny is in jail.
When they bury Killer the dog, Thurgood Jenkins lights a joint, then passes it to Brian; a second later, he again has the unlit joint in his hand.
When the guys are floating around apartment the Guy On The Couch is laying with is back to them, but when the guys float out the window and The Guy On The Couch begins floating he is facing outward.
In the "Mid Eighties" scene, a USPS mail Jeep is shown. The Jeep has a license plate on the back. Official USPS delivery vehicles have not used license plates since 1973.
Brian, Scarface and Thurgood hand out the samples at the club and after it is apparent that all were smoked, one of the "floating" people is swimming. You can see the wire harness on the back of his hip moving him along.
Dave Chappelle played Thurgood Jenkins and Sir Smoke A Lot. So when Thurgood went to Sir Smoke a lot's house, it was another actor playing Sir Smoke a lot when Chappelle was playing Thurgood and Vice-versa. When you see Thurgood first he has a earring in his ear. But when Sir Smoke a lot hugs him, the actor playing Thurgood has no earring in.
Mary Jane meets Thurgood, Scareface and Brian at the prison. When the three of them are sitting in Mary Jane's Jeep, before Mary Jane gets in the ignition sound (sound when keys are left in ignition when car is off) can be heard, yet her door is not open and her keys are in her hand when she gets in.
In the "Mid Eighties" scene, the boys light the joint with a Bic lighter that has a child resistant striker. These were not introduced until the late 1990's.
Pepsi bottles at the beginning with the new 1990s logo and not the old 1980s logo.
When Brian, Kenny, Scarface, and Thurgood are in a convenience store in the beginning of the movie, Brian is holding his head, asking everybody if they're OK. When we hear him say, "How you doing. Kenny?", his mouth doesn't move.
When Thurgood, Scarface, and Brian are flying towards Kenny's prison window. The middle window has an unedited green screen.
In the theater version, a boom operator, complete with mike, could be plainly seen crouching in the corner after Mary Jane slams her apartment door in Thurgood's face, and he tries to talk to her through the door. The crewman is directly behind Mary Jane's door, inside her apartment. Later, in the home-video version, this mistake was corrected, but the top of the crewman's head is still visible at the bottom of the screen.
When the cop is kneeling next to fallen horse "ButterCup" the black sandbags he tries performing CPR on are clearly visible.
Kenny comes out of a Pizza Pizza, where you can see a large Sam the Record Man, both of which are Canadian chains and are located in downtown Toronto, not New York.
When Thurgood takes Mary Jane on a date, she suggests they go for Chinese food and we see a shot of the restaurant sign. The movie takes place in New York, but the sign says "Licensed under LLBO", which is the Liquor Licensing Board of Ontario.
When Thurgood is unknowing sent to deliver weed to Mary Jane, how does he not know that that's her apartment?He's clearly been there before.
The calendar, which Kenny is marking, says it's November. But when the guy on the couch wakes up, Thurgood says it's August.
In the scene where the guy on the couch tosses the crumpled piece of notebook paper to Thurgood, as Thurgood is reading the note it is evident that the guy spelled sincerely wrong. He failed to include the second "e".