What does "crazy characters" mean?
We are now hitting the linguistic Great Divide: People whose primary language is English-- or, at most, a western European language-- and the rest of the world.
There is no inherent diffence between a Roman letter and a Greek or Cyrillic letter. If your text's primary language is English, you could test for non-ASCII or non-Latin-1 characters. But it gets trickier if you're working in a UTF-8 environment, even if it's just so you can use curly quotes without resorting to illegible and space-guzzling entities. Or if you need to bring in the occasional word in an Eastern European language. Then the non-ASCII characters won't jump out and hit you in the face.
(That's dialect-specific. I use it to check for things that can't be auto-converted from UTF-8 to Latin-1.)
Incidentally, curly quotes are in Windows-Latin-1, so they will be de facto recognized by most systems that profess to use ISO-Latin-1. There's an Official Pronouncement about it somewhere. But if I insert something like ο (Greek) or о (Cyrillic) the Forums will go haywire.