Take one drink if:
"Blondie" (Clint Eastwood) squints.
"Blondie" lights a cigar.
You hear an overly cheesy gunshot. (You can be exempt from the bridge battle scene since there are so many and you don't want to have alcohol poisoning.)
Someone on camera takes a drink.
Take two drinks if:
Someones head is in a noose. (and they're actually in danger of being hung.)
A woman is on camera.
Tuca "The ugly" makes the sign of the cross on himself.
