Sometimes even the best-laid plans can fall apart. Just ask comedian Bill Engvall. If his life had worked out the way he planned, he could be teaching your kids right now. Not that one of the country's top-selling comedians would have made a bad teacher. It's just that if Engvall's latest Warner Bros. release, Dorkfish, is any indication, his might have been a classroom populated by stories of prehistoric porpoises with huge overbites which cavemen caught with corndogs on a hook. It's not exactly your everyday lesson plan. Making audiences nationwide howl is just what this Galveston, Texas native has been doing since his Here's Your Sign album took the country music industry by surprise two years ago. Engvall, a club disc jockey-turned-stand-up comedian, suddenly found himself a platinum-selling artist, with both a gold single and album to his credit.