Zelgadiss: onlysanechimera - Zel's the straight man. He's usually the textbook Only Sane Man character (I picked the phrase up before discovering TV Tropes, actually - it got used in an essay about H2G2.)

Jak: precursorstone_gun_nest - a quote from Jak II. He says it when firing up a gigantic cannon to blow the Metal Head nest open. I think stone_gun_nest was probably better.

Leila: everything_is_dangerous - another quote. Matthew asks Leila not to take on anymore dangerous jobs. Leila replies, "We're spies, Matthew. Everything we do is dangerous."

Pretty Butterfly: papillio_tempestatis - Latin for "butterfly of the storm". I think I misspelled it - too many Ls. Weather-affecting butterflys crop up a lot in Interesting Times.

Maugris: angryyoungvamp - from the Billy Joel song "Angry Young Man".

Give a moment or two to the angry young man
With his foot in his mouth and his heart in his hand
He's been stabbed in the back, he's been misunderstood
It's a comfort to know his intentions are good.

Erk: dontcallmeerky - Not much to say here. Not actually a quote.

Rose: eagle_caller - Early in Martin the Warrior, Rose saves Martin's life by imitating an eagle's hunting cry to scare off seabirds. (They're mice, so seabirds are kind of a big threat.)