Via Josh, the sad story of American Dog.
Chris Sanders, co-director of Lilo & Stitch, my favorite animated film, originally developed American Dog for Disney until he was fired. Under John Lasseter, AD then became the current Bolt. (Thus guaranteeing I won’t see it.)
The last straw, according to the AD link above, is that original creator Sanders is nowhere mentioned in The Art of Bolt coffee table book. In response, that site has posted their own art gallery of concept art and early works.
Sanders also has a webcomic, Kiskaloo, where the cat character resembles the original supporting feline from American Dog.