I'm reading an old Green Day interview from Spin magazine (1995) and I think you all will appreciate this description of Billie:
"Befitting his funk, Armstrong's dressed all in black: black cashmere sweater, black Dickies - 'I've had these pants for four years,' he boasts - and a black on black pair of canvas Converse. His 5'7 frame, downsized further by a perpetual slouch, keeps him soft and approachable, cuddly even. "
And here's a description of what Billie does when he's bored:
"I watch as Armstrong gingerly pushes a puddle of drool over his bottom lip and toward the ground, only to slurp it back up into his mouth before the connection gets severed. He repeats the gross-out parlor trick again and again, solely for his own amusement."
Pretty spot on if you ask me