When David and Rocky are beaten up in an alley, David is wearing a sweater, but when he changes into the Hulk, the sweater looks more like fabric.
When the gang attacks David a second time when he's with Rocky, and they are shoved into a brick wall, the entire wall bends. This happens twice.
The plot depends on 'Rocky' taking several swallows of drugged water during a round - but boxers never drink during a round, though they might rinse their mouth and spit it out. (They do, however, drink water between rounds.) Taking in water during a hard workout can result in stomach cramps.