Fat Wizard's point, click, and drag design makes it a pretty accessible experience, and I really dig its Adventure Time-esque aesthetic and goofy voice-overs. The "artifact" modifiers earned during gameplay add a bit of longevity to it, but I do think that a stage select option would've really helped. As is, every "Game Over" boots you back to Level 1 -- but you do get to keep your artifacts, so it's not too tough to work your way back.
You'll undoubtedly find deeper tower defense titles with little more than a Google search, but I'd still recommend Fat Wizard to those of you looking for a cute, quick distraction that doesn't require too much of an investment of brainpower or strategy.
Estimated playtime: 30 minutes.