The movie is set in 1978, but as the cast arrive in Detoit for the concert a Barry Sanders of the Detroit Lions wall mural can be seen among the cityscape shots. He didn't play for the Lions until 1989.
In the beginning of the film, a Misfits poster is seen on the ceiling. While the film takes place in 1978, the Misfits did not use the Crimson Ghost logo until after the release of the Horror Business single in 1979.
When Trip rotates the comics rack in the corner store, the following comics can be seen: Incredible Hulk vol. 1 #231 (cover date January 1979) and Master of Kung Fu #73 (cover date February 1979). Though it's likely these issues were initially published in November and December 1978 respectively, the movie is clearly set during the summer of 1978.
Right before Kenny and Bobby pull the boys out of the car, the camera shows Christine blowing a bubble with her gum. But, when Kenny and Bobby are shown again, you can clearly hear Christine's bubble pop.
When the scalper is directing Edward Furlong to the stripping contest to win the money to buy a KISS ticket, the scalper has a cigarette in his mouth. The shot quickly cuts away to a different angle and the cigarette is gone but magically reappears in his mouth again when the shot returns to the original angle.
After beating up Kenny, Hawk joins the other three in front of Bobby. As Hawk walks over in this wide shot, we see Lex start to reach for his belt to take it off. A couple shots later, in a close-up of Lex, his hands are at his sides and then again reach to take off the belt.
At the restaurant where Beth is eating with her parents there is a cruet of vinegar on the table. This never happens in the United States, but it is common in Canada where vinegar on french fries is quite common.
When Jam gets his foot stuck in the bullworker, which also has the foot of the bed stuck in it, he pulls on his foot, and the other side of the bullworker releases and hits him in the face. If the bullworker was really stuck on the bed, the bed would have to have been lifted up for the other side to release.
When the mother picks up the record from the turntable she is looking at Side 2 of the KISS album, "Love Gun". "I Stole Your Love", the song that almost blows her through the chair, is the first song of Side 1.
In the entire movie, the concert was to take place at COBO Hall, which is a banquet hall, and a Kiss concert was never performed at COBO Hall. To be correct the concert should have taken place at COBO Arena, right next door.
When the boys go to the ticket-taker, and Jam says "Are you f***ing kidding me?", he motions to the boys with his hand, and we can see that his knuckles are cut and bloody from beating up the other boys. But, if they were just mugged, his knuckles wouldn't be bloodied up.