[GeronL]

What exactly has mark Hamill been doing?

Voicing animation?

[x]

Tweeting for one thing.

[Future Snake Eater]

Mark Hamill is the definitive voice of the Joker. He's recently retired from that particular gig, but he's very well-known for it.

He also played the lead role in "Wing Commander III" and "Wing Commander IV" which were some of the earliest big-budget PC CD-ROM games to be filmed as movies. He was actually very good in those, too.