There's only one thing more fashionable than a Louis Vuitton purse — and that's a Louis Vuitton purse with an itty-bitty dog sticking out of it.

Inspired by Paris Hilton's Tinkerbell (search) and Reese Witherspoon's (search) well-dressed Chihuahua, Bruiser, in the "Legally Blonde" movies, trend-setters like Britney Spears and Jessica Simpson are scampering to the pet store to buy teensy-weensy teacup and toy dogs — and fashionable carriers to tote them in.

"Everyboy has them now," said Susan Bing, co-owner of Trixie and Peanut, a popular New York City pet boutique frequented by celebs like P. Diddy (search) and Milla Jovavich (search). "It's a trend that kind of got started and was encouraged by the 'Legally Blonde' movies. And of course it helps having celebs like Paris doing it."

Besides Hilton, described as the "patron saint of doggy boutiques" by one Beverly Hills store owner, other celeb-teeny dog pairings include Adrien Brody (search) and his Chihuahua, Tori Spelling and her pug, Jessica Simpson and her new malti-poo (a Maltese poodle), Britney and her Maltese and P. Diddy and his Maltese.

Bing says the really "in" dogs are Maltese, Chihuahuas and Yorkies.

"The trend is the smaller the better. Everybody wants the teeny, teeny teacup dogs, 3-4 pounds and under," she said. Bing added that the mini mutts start at about $1,500, the smaller the pricier.

And with the increased demand for little dogs has come an increased demand for stylish totes to carry them in, among other goodies.

"The dog is viewed as an accessory, and carrying the dog is an opportunity to dress the dog and make the dog look fashionable," said Mike Campbell, owner of the just-opened Doggie Style boutique in Beverly Hills.

While Paris and Reese have made it cool to dress pooches in sweaters and designer collars — a pastime Bing said was once reserved for "kooky old ladies" — the really hot items among fashionistas are dog carriers that look like handbags.

"We have so many people now who want carriers that look like purses, we've been special-ordering them," Campbell said.

Indeed, Bing said high-end designers like Ralph Lauren and Donald Pliner (search) are now making pooch purses, along with Louis Vuitton, Kate Spade and others.

But why little dogs? Experts say they're easily transportable for people on the go, fun to dress up and loving companions that fill a void for adults who don't have kids.

"They're not ready for children yet, so it's like having a baby — there's a sense of great responsibility," said Wendy Diamond, editorial director of Animal Fair magazine, which features Paris and her equally famous Chihuahua on their latest cover. "More people in the U.S. are single and living older. Dogs are their children."

L.A. fashion expert Elycia Rubin said dog as man's or woman's best friend is the "ultimate accessory."

"It's comforting, this little creature that loves and adores you. You get constant security, love and companionship. And guess what? Dogs get you a lot of attention."

Dr. Bernadine Cruz, a California veterinarian who specializes in small animal medicine, said the tote-your-dog trend is totally healthy, as long as certain rules are obeyed.

"The bonding is marvelous — small dogs [allow for] tighter bonding. But they still need to be well-behaved — come, sit, stay and the rest of it. Doggy handbags are fine, but some [doggy] attire could obstruct them, or they could rip it off and swallow the fabric. And daily exercise is very important — little dogs tend to get very fat."

Bing also warns against breeders who specialize in small dogs, as malnutrition could be a concern.

But is it normal to treat your dog like a baby? Cruz says it can be.

"As long as you realize that this is an animal, a pet, then yes, you may treat it like a child."