Let's do some good old character cast typing.
You can watch full episodes in HD here: Fringe - Home
unless you have a mac...
then their going to want you to get a flash update that rapes your computer and doesn't allow you to watch the episodes.
The only characters I'm really sure on are Walter Bishop, Peter Bishop, and Nina Sharp.
Olivia Dunham - I*F*
Peter Bishop - IS*P
Walter Bishop - ENTP
Lance Reddick -
Phillip Broyles -
Charlie Francis -
John Scott -
Nina Sharp - ENTJ (of course)
Astrid Farnsworth - *SF*
Olivia comes off as an S, even though she say's that he's awesome at recognizing patterns which is an N specialty.
All I really wanted to say is the Walter is a complete ENTP.