Good Piece of Artwork.
Okay, for those who are young out there:
(In order from left to right):
~( Possibly ) Gunnery Sergeant Hartman from Full Metal Jacket.
~Red Skull from the Captain America comics / television show.
~Darth Vader ( or James Earl Jones wearing a Darth Vader costume ) from the Star Wars franchise ( even the young ones should know this ).
~Frankenstein's Monster ( Not Frankenstein, you imbeciles ).
~Shredder from TMNT.
~Cobra Commander from G.I. Joe.
The joke could be that Red Skull was a Nazi, and would never join the Army, that Darth Vader is supposed to be missing his legs and his left arm, that Frankenstein's Monster isn't a bad guy, that Hartman is scared of a couple of bad guys... Heck, maybe even none of the above.
The ironic part is, I'm only a teenager, and I know all of these guys... I think...
I guess that I'm a geek.