Can drinking alcohol (not excessively) cause a seizer?!
Answers: No, probably not. It's more likely to prevent seizures than to cause them. It slows down the firing of the synapses, and a seizure is a misfire. Also, I have read statistics that say many epileptics become alcoholics because they regard drinking as a reliable method of seizure prevention.
If drinking excessively, some people get low blood sugar and they have seizers called Hypoglycemia. It says even some people just drink one, they have this muscle convotions and twitches
Hypoglycemia can be triggered by alcohol, but I've known heavy drinkers who were so diabetic that they eventually had insulin pumps installed in their bodies, and none of these people ever had such effects from alcohol, so I'd guess that it's probably pretty rare.
Another possibility would be an autoimmune disorder which could cause a severe allergic reaction to alcohol. The most common allergy of this type is allergy to peanuts, which is itself pretty rare in the more severe forms, so again this is something you aren't going to see much outside of House, M.D.
Real-world, if a seizure was triggered by a small to moderate amount of alcohol, my best guess would be that the drinker was epileptic. While some epileptics can drink heavily without triggering seizure, it's not all to rare for someone to have epilepsy which can be triggered by alcohol.