Ponytail: Eh. It’s okay. Occasionally it’s cute, almost like a bunny’s tail.
Long hair, 2012 style: Perfectly okay, most of the time. Occasionally slightly unfortunate.
Long 1990s hair: LOL.
Short 1990s hair (various versions): Yum.
Short hair and beginning beard (ca. 2001): Even better.
2003 hair: cute. The most pixie-like he’s ever looked.
Eraser-era hair and beard: YES PLEASE.
2009/2010 hair: I’d consider taking up residence in that, too.
Bonus answer to the obvious question:
Headband: Oddly endearing.