Turns out that retrograde amnesia is the greatest thing that ever happened to Samantha "Sam" Newly.

The title character in "Samantha Who?" was a completely awful person. But when Sam (Christina Applegate) is run down by a hit-and-run driver, spends eight days in a coma and wakes up, she can't remember anything about her life. And when she finds out about her life, she's horrified.

"At first, my problem was that I didn't know who I was," Sam says in tonight's premiere (8:30 p.m., ABC/Ch. 4). "But now, my problem is that I do know who I was and I really hate it. And I really want to change but maybe I can't."

"Bad Sam" was mean, nasty, vain, self-absorbed, adulterous, back-stabbing, avaricious — you name the vice, she had it. "Good Sam" seems like, well, a pretty nice person with a whole lot of baggage she can't even remember.

This is not a comedy about someone who is going to eventually recover her memory — creator/executive producer Donald Todd assures us that Sam "will not ever fully regain it," although there will be "opportunities for her to recover a little memory at a time."

Mostly bad ones, as it turns out.

"Bad Sam" was estranged from her self-absorbed parents (Jean Smart and Kevin Dunn); she's cheating on her nice-guy boyfriend (Barry Watson); her best friend (Jennifer Esposito) is a drunken tramp; and the one friend who sticks by Sam (Melissa McCarthy) has really been Sam's friend since elementary school.

She's never even spoken to her doorman (Tim Russ), but when she does it turns out he's a really nice guy (once he gets over the shock).

Sam has pretty much been horrible to everyone around her.

She is aghast as she finds out more and more about herself, but she's determined to become a better person. Although there are moments when "Bad Sam" unexpectedly (and rather hilariously) comes out.

And the whole amnesia thing is by no means a tragedy — it's a blessing.

"That's exactly how we're approaching it," said Todd, "is that it's the idea of taking an infirmity, a problem, and making the best of it. She has to realize that. At first ... she just wants to get back into her life. That's what a person would want to do. But gradually, through the friends and experiences, she realizes that — who wouldn't want this opportunity?"

It certainly helps that Applegate is so great in the role. And there is some very funny stuff in "Samantha Who?" The pilot is pretty good, and a second episode sent to critics is even better — a very good sign.

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