Are you sitting down?

Two of the best new shows on TV this fall are on UPN, which hasn't put two really good shows on the air in its 10-year-history.

You could knock me over with a feather.

But "Kevin Hill" and "Veronica Mars," along with a pair of ABC shows and the WB's "Jack & Bobby," are this fall's most promising pilots. Even UPN's third show, "Second Time Around," isn't bad.

On the other hand, the WB — which has, unlike UPN, built a reputation for quality programming — doesn't have much to hang its hat on this fall aside from "Jack & Bobby." The WB's new shows include a pair of stinkers and one that is still an unknown quantity at this point.

Here are the two networks' new shows:

Jack & Bobby (Sundays, 8 p.m., WB/Ch. 30) is a teen drama with a fantastic twist. It's the story of two brothers — last name McCallister, not Kennedy. One will grow up to be president; the other will not be alive to see his brother take the oath of office.

Jack (Matthew Long) is an all-American teenager who's idolized by younger brother Bobby (Logan Lerman), who's a bit of a geek. The two are the center of the world for their mother, Grace (Christine Lahti), a domineering, driven, yet vulnerable college professor who's more than a bit difficult.

This is, in many ways, yet another good teen drama from the producers of "Everwood." But the hook is that future-president thing, and the chance to see how a visionary president's character was formed. The episodes are intercut with scenes more than four decades in the future as some of the characters talk about the recently completed McCallister administration.

The big question is whether succeeding episodes can be uphold the quality of the premiere.

"Jack & Bobby" premieres Sunday at 8 p.m.

Second Time Around (Tuesdays, 8:30 p.m., UPN/Ch. 24) features real-life couple Boris Kodjoe and Nicole Parker as a fictional pair of newlyweds. Well, sort of newly — they've just remarried several years after their divorce, which followed a brief first marriage. Various friends and family members complicate an already somewhat complicated situation, with hopes that laughs will ensue.

It's not bad. And Kodjoe and Parker make an appealing couple. But what laughs there are in the pilot episode — and there aren't many — are forced.

"Second Time Around" premieres Monday, Sept. 20.

Veronica Mars (Tuesdays, 8 p.m., UPN/Ch. 24) is sort of Nancy Drew for the 21st century — smart, attractive, intuitive and tough 17-year-old who has a particular talent for solving mysteries. By day, Veronica (Kristen Bell) is a high school student. By night, she's the brains behind her father's (Enrico Colantoni) detective agency. The cast includes a bunch of other teens — an ultra-rich in-crowd and a lower-middle class out-crowd — who inhabit a seaside town where there are secrets aplenty. Including the mystery of who killed Veronica's best friend, an ultra-rich girl whose murder remains unsolved.