Here's a look at what they'll bring to this month's madness.
Name: Joe Bruin
Origin: Started as cub in UCLA Den
Natural Enemy: Trojan
Joe Bruin might look cuddly, but he's no Teddy bear. This bear has claws.
UCLA's mascot grew from a cub to an adult bear in the late 1920s, after waking from his hibernation in the shadow of the fearsome Cal Bear. Joe has been through several changes during the past 90 years.
The key has been striking the right balance between growling, slobbering predator and friendly furball. Here's an excerpt from an October 2005 article in the Daily Bruin newspaper.
Local news from across Southern California
"In 1970, the logo was transformed into the most familiar of all incarnations: the broad smiling Joe with the tilted head that appears as Joe and Josephine Bruin on the sidelines of every football and basketball game... Each version of Joe Bruin has its followers, and developers have attempted to reach a compromise between the tradition of a friendly Joe with demand for a more aggressive mascot."
Joe finished at No. 8 in the 2008 Capital One Mascot Challenge, a contest in which fans vote for their favorite mascots.
University of Southern California
What: Andalusian horse
Origin: 1961 Rose Parade
Natural Enemy: Bruin, hardwood floors
Facebook Page: Hooves make it difficult to update status using traditional keyboard
Horses do not get along with basketball courts, so USC's basketball mascot is a far whinny from what we see at the Trojans' football games.
The tradition of USC's noble horse, Traveler, dates to 1961 after Richard Saukko was noticed riding a white horse at the Rose Parade. During USC's home football games, a Trojan rides triumphantly around LA Memorial Coliseum on Traveler -- the school's official mascot.
To avoid serious injury to humans and horse, Traveler is not allowed on basketball courts. The Trojan mascot will have to rally the crowd while his best friend stays at the hitching post during the NCAA tournament.
As for Tommy Trojan, he will stay put on the USC campus.
California State University Northridge
Origin: 1958, selected by students
Natural Enemy: Clever bulls
Matty the Matadaor actually pre-dates his school. Cal State University Northridge was San Fernando Valley State College when students selected the matador mascot in 1958.
He sports a confident smile and prominent chin. Don't let his nasty reputation in the Big West Conference fool you, he's a very approachable mascot as stated on his Facebook page.
"I love meeting the fans, so next time you see me at a game, holla at me and let everyone know which team has the loudest and best fans in the nation!"