Doting pet owners have long pampered their critters with gourmet food, fine bedding and even massages. A growing number are now dressing them up in pet costumes for Halloween trick-or-treating and pet parades. Pet stores and online costume retailers several of which have formidable animal sections are seeing a surge this year in requests for such costumes as Superman, Giddyup Cowgirl, Top Dog Tuxedo, '60s Hippie and Hell's Angels Biker. Why the new market? Explains Shari Maxwell, owner of the online AnniesCostumes.com, whose pet business doubled in the past year: "Now when parents go out to dress the family for trick-or-treating, they feel bad if they leave out the pooch." Usually ranging from $10 to $20, the getups are at least a little cheaper than dressing up Billy as Spider-Man. And if you can't prepare your pet for Halloween, there are other holiday dress-up opportunities. They include Shalom Pup (blue Star of David scarf and hat) and Santa Claws.