I did this for the UK convention 'Amecon' (www.amecon.org) along with various other bits of art and animation - this one was used on the back of the 2006 conbooks.

 This one was inked by hand and then scanned in and coloured with Adobe Photoshop. I think I completed the whole thing in 3 or 4 evenings after work but it was done in October 2005 (over a year ago now) so I can't quite remember. They say the memory is the first thing to go ;)