Revealing mistake: In the beginning of the movie, when Pee-Wee's breakfast contraption is running, if you look closely at the "orange" that is being squeezed, it is really an orange coloured sponge ball. (00:05:10)
Revealing mistake: When the pancakes are sticking to the ceiling, you can see that when one hits the ceiling, it jumps. The pancakes were actually being dropped on the floor with an upside down shot. (00:05:45)
Revealing mistake: In the scene where Pee-Wee is face to face with Professor Tanaka asking for Francis' whereabouts, the background behind Pee-Wee turns into an obvious painting on a set between shots. Notice how all sunlight and wind vanishes when he shouts "Where are they hosing him down?" (00:22:15)
Revealing mistake: When Pee Wee is driving while Mickey is sleeping, he is passing all these signs that warn the road is going to become curvy. If you look at the bottom of the signs, you can see they are being moved on a track while the camera stays stationary. Full screen only. (00:38:30)
Revealing mistake: When Mickey drops off Pee Wee in the middle of nowhere he hears animal sounds all around, so he reaches for his headlight glasses and puts them on. All the animals except for a few small critters like raccoons are all fake. (00:40:55)
Revealing mistake: After Pee-Wee tears through a Godzilla production in the Warner Bros. studios with his bike, he exits the stage, ending up on an alley where he turns left to evade the props and security guards on his tail - one of which has a motorbike. On the pavement beneath him is a curved skid mark from a previous take, not unlike the one left behind by the motorbike seconds later. (01:15:40)
Revealing mistake: The entire snack bar cartoon sequence shot at the drive-in theater during the world premiere of "Pee-Wee's Big Adventure" is actually a montage of different shots patched together, and it almost looks completely seamless until you focus in on the car farthest right. Notice how the passengers change positions every time the shot changes on the drive-in screen. (01:21:00)
Revealing mistake: Throughout the studio scene where Pee Wee is shot from the front being chased by security, the fact that his bike is on a rig can be seen by how rigid the bike is when he pedals it and it doesn't move side to side like it does when he's riding it freely in all the other shots.
Revealing mistake: After the bar scene where Pee Wee leaves riding the motorcycle, we can see it's a stuntman, given the different physique of having wider shoulders and a fuller head of hair than that of Pee Wee.
Answer: It was some sort of gag gum (popular in the past) that either had hot pepper/cinnamon or simply tasted terrible.
Brian Katcher