Factual error: It is not possible to be "allergic to all known anaesthetics". Amongst the amide local anesthetics lidocaine, prilocaine, bupivicaine, mepivacaine and dibucaine are naturally occurring substances and if administered without a preservative they cannot trigger an allergic reaction. If Bales is allergic to them, he'd be allergic to the metabolic processes of his own body. They are all powerful local anaesthetics and could easily be used for a radical rhinoplasty such as that required by Bales.
Factual error: When they are putting out the fire, Charlie belts out "I want two 2-1/2 inch lines from the pump to the fire and three 1-1/2 inch lines from the hydrant to the pump". This is backwards. No fire department would ever use three small handlines to supply an engine from a hydrant.
Factual error: Early in the movie, CD and Roxanne are carrying her telescope up an external stairway. The scope is what is called a Newtonian, it's on a German equatorial mount and it's fully assembled. If she really were a professional astronomer she would never attempt to carry the scope assembled to the fragile German equi. mount. It is very easy to dismount the scope, carry it up separately from the mount, then reassemble up top. This would significantly reduce the possibility of damaging the very expensive mount.
Continuity mistake: When Charlie is going through his comebacks with the guy in the bar, right before he gives the last one he is seen from a distance standing next to the guy, then he starts and the scene changes to a close up and he is now leaning against the table that's up against the wall.