Boo is Largo's concience. Here I'll give you some links to the good boo strips.... (Its only fitting that Boo is Largo's concience since he is both very l33t and a BG freak.)
Boo's First Appearance
Largo and Boo meet
Only partially Largo and Boo related...
Boo and Largo in the sewer
B + L Unleash an ancient evil
B+L Follow the Evil
B+L Plan
yet another strip
Getting weapons
Boo tries to get his old job back
Boo lost Largo
Boo revives Largo's l33tness
B+L in the arcade
9-11 Sad Boo
Big Boo
More boo-ness
And umm I think thats all the strips with boo in them of
MegaTokyo that there is, but I really think you should just read them All rather than these links... geez was I ever bored to have done that...