Who would have thought Fido fashion would become so doggone popular?

There was a time when puppy dresses and jewels were reserved for the canine companions of heiresses and kooky old ladies. But nowadays it seems every Spot, Rex and Patches has a wardrobe to call his own.

"We started out a few years ago with a small selection of dog clothes, and the demand was so high that we opened a whole section called 'Up on the Woof,'" said Orlando Veras, spokesman for Macy's Herald Square in New York City. "[It] sells everything from dog clothes — which range from $20 to $50 — and their human equivalents to accessories and treats."

"People from all over come here specifically for our [dog department]," added Veras, who is currently gearing up for Macy's annual Bark Fest, a benefit that invites dogs and their owners to party with pet psychics (that's right, pet psychics) and trainers.

Macy's isn't the only national retailer fetching a piece of the dog-market Frisbee. Target, Wal-Mart, Sears and Old Navy have also decided to take a bite out of this multi-billion dollar industry.

But in spite of the mainstreaming of a trend once reserved for Paris Hilton, Britney Spears and goofy grannies, naysayers find doggie indulgence anything but normal.

Guy Puglia, 33, has had his pit bull Shiva for seven years — but he's never dressed her up and never plans to.

"It’s a dog, not a person — maybe a jacket when it’s cold out, but never clothes," he said. "That’s just people not having kids and making their dog a person because they have no life. It’s very ridiculous — especially people who paint their dog's toenails."

But the dog industry has proven so lucrative that designers and business executives alike have decided to boldly go where no man has voluntarily gone before: the doghouse.

"In the past three years, this [sector] has seen an incredible boom. People really want to spend money on dog clothes, beds, treats and accessories," said former Morgan Stanley financial adviser Elliot Gordon, who recently left the money world to be where the money's at.

"I bought The American Dog Club store back in September 2005. I just loved what was happening in this market," said Gordon, whose store in Albertson, N.Y., sells everything from moderately priced faux Burberry dog bows to $350 genuine Faberge Egg dog beds.

"We sell designer bags to hold poop bags for $16.99. Two years ago, nobody would have bought that."

While many of Gordon's products fall on the side of extravagant (he sells $200 chenille dog beds and Juicy Couture dog carriers), the beauty of this industry's evolution is that there is something cute and over-the-top for every budget.

"Retailers like Target are increasing their merchandise space to go with this trend. They are just offering lower-end products," said Gordon.

Items like the $12.99 Posh Wash Pet Manicure set, which includes polish and emery board, and Leopard Print Dog Pajamas for $14.99 to $18.99 are examples of Target's affordable pet luxuries.

Similar items can be found at Sears.com and Wal-Mart, both of which offer sassy, budget-friendly dog paraphernalia like bejeweled dog collars and flannel jammies.

And if you think this trend extends to soft and cuddly mittens, you're barking up the wrong tree.

"Cat owners spend zero," said Gordon. "Dog owners spend money because their dogs often become the centerpiece of the family."

According to the American Pet Product Manufacturers Association's (APPMA) National Pet Owners Survey, dog owners are the most lavish spenders, accounting for over 43 percent of the pet industry's $35.9 billion worth of sales.

While a good portion of that spending is on grooming and veterinary bills, a substantial chunk can be attributed to decadent dog treats, pint-sized pooch apparel and beds to bark about.

Bowwow fashion certainly seems to have dug out a permanent place for itself in the world of retail. But Puglia thinks there's no excuse for dogs that are better dressed than their owners.

"Some people spend more money on their dogs than they do on themselves," he said. "I've seen dogs with Gucci jackets, even Coach. I don't understand."