The problem with the unknown letters are they're so bizarre it's hard to guess what they are. Perhaps a mix of letters and numbers? I say that because there doesn't seem to be any logical word it could be when you assume the rest of the letters. Has anyone managed to grab the message from the hand tattoo picture?
Also, what are people's opinions on the relevance to the music being used in these videos? I mentioned yesterday, if I'm not mistaken, that these are new compositions. Are they relevant to the puzzles? Any hidden clues like Morse code etc? Or are they just cool remixes made specially for these videos?
EDIT: Just before the letters appear across the middle of the screen, they flash at the top, and appear to be more clear. In this screengrab I can make out "e d e" Note the flick of the middle letter which I think is a d, at the top extends onto Abe's forehead, and flicks out at the bottom right. I believe it's the part of the phrase after the "l i k". So as a whole it'd be;
"e l i k e d e ? ?" Still missing a few characters. Here it is nonetheless:
SECOND EDIT:
So I got home and I decided to give my idea a try of re-warping the image in photoshop to undo the bend that has been applied to the letters. The letters match up with the portion that appears in the other image I posted. Here's an image of them warped into place, and then with my interpretation marked on top:
The "d" gets a bit lost in Abe's face there, but it's safe to assume that it's a d from the first picture in my post.
Compare all the images and see if you agree. I think the phrase reads "e l i k e d e t s" but that means nothing so it could well be wrong. Sorry about the garbled post.