One problem with community theatre is that you don't always have a lot of choices in the casting pool.
I was in a production of One Flew Over the Cuckoo's Nest a few years back. I played an orderly (I was 18 at the time). The guy that played McMurphy was the right age, but the guy that played Billy Bibbit (the stuttering kid, that's supposed to be about my age) was in his late 40s. He wasn't a bad actor, but it still felt a bit odd.
Also, the guy that played the doctor was an alcoholic, and twice during performances I had to run offstage and wake him up to come on while everyone else ad-libbed to try to make his absence not noticeable.