You can do this with pretty much any semi professional painting program and a drawing tablet/display - procreate, photoshop, Krita, corel paintshop pro, etc. I looked through his website and couldn't find anywhere where he said what he used, and there isn't enough evidence to say one way or the other.
My favorite little known factoid is that when I googled his name Wikipedia says he's the guy who drew the pastafarian parody of The Creation of Adam, title "Touched by his noodly appendage".
My favorite little known factoid is that when I googled his name Wikipedia says he's the guy who drew the pastafarian parody of The Creation of Adam, title "Touched by his noodly appendage".