When Banner becomes the Hulk during the magic act, the creature and his tattered clothing are dry despite having been completely submerged in water.
At approximately 34:30 in, Jasper is having an asthma attack in the motel room, he uses his emergency inhaler first by taking 5 rapid puffs, pauses, then another puff, pauses again, then takes a final puff. That is an overdose that, combined with his heart condition, could easily have caused a fatal heart attack. The correct maximum dosage would be a single puff, then after waiting a full minute, ONE more puff. Then to be safe he could repeat that after 4 to six hours. Especially in the 1970s where the medication in the inhalers worked by stimulating adrenaline in the body and rapidly increasing one's heart rate and the strength of the heartbeat.
At the end when one of the guys in white picks up a 'heavy' stone slab to hit the hulk (44.15) the slab bends slightly upon contact with the hulk's body. Obviously it is made of plastic or fibreglass.
When the hulk breaks out of the car at the end, grabs the guy in white and throws him, the spring-loaded platform catapulting the guy is visible under the guy's feet (43.20)
When Jasper does the trick with the magically appearing candlestick, we the audience couldn't see the trick, but David and some customers were behind him, so *they* could have easily seen what was happening behind the cloth. The director should have staged it so that everyone was in front of Jasper.