Continuity mistake: When Cheech pulls down his cap in front of his eyes and shouts "I'm blind" you can see some cars stop beside them. When it cuts the cars are gone. (00:17:30)
Continuity mistake: When Cheech and Chong come into the courtroom, the judge takes off her glasses and holds them. When it cuts, she isn't holding them anymore. (00:18:30)
Continuity mistake: When Cheech and Chong get to the courtroom, there are two pencils on their table. When Chong falls to the floor, no pencils are to be seen. (00:18:35)
Continuity mistake: When Cheech says "He's right man, these are lame" to Curtis, one of the band members is standing behind Curtis. When it cuts to a closeup of Curtis, the guy is gone. (00:21:25)
Continuity mistake: When Chong is on the phone with Cheech and about to go outside you can see a man in a white hat dancing by himself. When it cuts the same man is dancing with a woman. (00:31:00)
Continuity mistake: When Curtis is talking to Cheech about his car and says "you got a taste of soul", Cheech is standing with both his hands in his pockets. When it cuts, Cheech suddenly has a hand scratching his chin. (00:34:25)
Other mistake: When Cheech and Chong are crossing the street talking about Cheech's uncle, two buses are coming. When the second bus passes by the camera, a kid on the bus waves his hand to the camera. (00:38:15)
Visible crew/equipment: When Cheech and Chong get to the border, Cheech spots some nuns in the car beside them. Watch closely in the window of the van when Cheech is looking at the nuns. You can see a man standing there looking at something and then looking at the van. This man wasn't standing there when there was a wide shot of the scenery. (00:44:45)
Audio problem: When Cheech and Chong are being questioned by the officer at the border, the officer says "you got any narcotics, any marijuana in here?". His lips continue moving but we can't hear him. (00:45:45)
Revealing mistake: When the cop on the motorcycle pulls Cheech and Chong over, one of the hippie girls is sitting in the front with Chong. Chong orders her to get in the back. She goes back behind the curtains and sticks her head out front. He pushes her back again. In a shot from the back of the van, you see Chong pushing her back, but you also see through the crack in the curtain that it is totally dark in front of the van. Since there is daylight outside, it shouldn't be totally dark. (01:00:25)
Revealing mistake: During the Battle of the Bands, when Cheech is playing his electric guitar it is not plugged up. Also, his voice is echoing through the stadium but he's nowhere near a microphone. (01:15:20)
Continuity mistake: When the band is done playing, sparks shoot out of Cheech's guitar and the guitar is burning. When it cuts, the guitar isn't burning anymore, then it is burning again. (01:17:35)
Continuity mistake: When Cheech stops to pick up Chong, the driver's window is down. A moment later, it's up.
Visible crew/equipment: When Chong gets into the Beetle and drives it out of the garage, the shadow of an arc light can be seen on the car.
Continuity mistake: The drum kit is a Ludwig amber Vistalite (see Keith Moon, who had a clear one, and Karen Carpenter, a blue one, neither had bottom heads) like John Bonham played in the Song Remains the same. The drum head on the kick drum in the back seat is on and off in the same scene repeatedly. They're a pain to remove, so it's physically impossible to do so and replace in the same conversation.
Answer: The lead singer is Rick Wilder. The band is credited as "Berlin Brats" (The Groups). The song is called "Psychotic", or sometimes listed as " (I'm) Psychotic", but it seems the middle part was cut out for the film or maybe arranged differently for the film.
Bishop73