I remember watching adam savage talk at maker faire and saying the whole expression, which not many people know, is "jack of all trades, master of none, though often better than master of one." A good example of something being good, then bad, then back to good again.

I dont think wormwood is from the bible. the 10th anniversary book pictured has a bunch of little facts about individual strips and characters from watterson himself, and he says pretty much exactly the same story about the screwtape letters.