Who's Yer Mutant Daddy? Eh??? Who's Yer Dad-deeeeeey???
"Blink And You'll Miss It" Dept.:
The guy on top, cutting his lawn until Jean Grey telekineticly "borrows" his mower is none other than Chris Claremont, father of the New X-Men.
The guy with the hose issues is Smilin' Stan Lee, carrying on from his previous Marvel movie cameos as "Hot Dog Vendor", "Guy Who Saves Kid From Falling Rubble", "Sleazy Sunglasses Vendor", "Old Guy Saved By Matt Murdock That Results In His Blindness", "Willy Lumpkin" and others.
Stan discusses his cameo in X3 and others in "COMIC CREATORS DISCUSS THE X-MEN" a book of interviews by Tom DeFalco published by Titan Books this month. Interestingly enough, according to interviews I've read with both of them, both Stan and Chris got into comics because their acting careers never took off - no word of a lie.
The source for these pix is the previously posted Ian McKellen Interview with Jonathon Ross.