Good Guys Gone Bad

When Bryan Cranston steps into the role of pistol-packing meth manufacturer Walter White on "Breaking Bad," he'll be erasing all traces of sweet, hapless dad Hal from 'Malcolm in the Middle.'

That's not a bad thing. It's fun to see some of our favorite do-gooders put on the black hat, and by all accounts it's fun for the actors as well. Some of television's most famous villains started out playing good guys; we've collected a few in this gallery.