Chris Forte, manager of the chic South End boutique Market, has a simple remedy for a bad day: throw on a little Julius the monkey.

"You can’t possibly be in a bad mood if you put on a T-shirt with a big monkey on it," Forte insists. "It’s something that makes people smile."

The big monkey of which he speaks is Julius, the whimsical creation of West Coast designer Paul Frank. Previously, Julius — he of the fat cheeks and goofy ears — rarely made appearances in the urban jungle. These days, however, the monkey has moved to Main Street. He’s popping up everywhere.

Call it guerrilla marketing, but the designer has attacked the streets with understated gusto, only allowing certain stores, the right stores, to carry his line of playful animal-print duds and accessories. A mere handful of those stores exists in Boston. At these shops, you’ll find Julius’s face on undies, change purses, umbrellas, PJs, watches, and T-shirts, as well as on the newly launched men’s line.

Market stocks the full line of menswear, complete with zip-front hooded sweatshirts ($95) and colorful T-shirts ($25). Newbury Comics and its sister clothing store Hootenanny offer a plethora of Julius paraphernalia. Most popular, says senior buyer KT, are accessories like coin purses ($14), umbrellas ($13), belts ($26–$36), and slippers ($17.50). Girls in particular are going ape for them, she says. In the Newbury Comics offices, KT’s co-worker Terry wore her Julius the Monkey T-shirt three days — three days! — last week. "It’s just because they are so cute!" KT explains.

Ozone also carries the ape-tastic wares, for both him and her. "It sells great," says store employee Tim. And Urban Outfitters sells a Julius watch with a blue strap ($100).

"He’s taking over the world," jokes Forte. "I think Julius should be our next president."

Nina Willdorf can be reached at ninawilldorf@earthlink.net

Where to find it:

• Hootenanny, 36 JFK Street, Cambridge, (617) 864-6623.

• Market, 558 Tremont Street, Boston, (617) 338-4500.

• Newbury Comics, various locations, www.newburycomics.com.

• Ozone, 336 Newbury Street, Boston, (617) 421-4464.

• Urban Outfitters, 11 JFK Street, Cambridge, (617) 864-0070; 361 Newbury Street, Boston, (617) 236-0088.

• www.paulfrank.com.