Often, one actor playing multiple roles is little more than a distracting gimmick (you won't remember this, kiddies, but every '70s sitcom seemingly had a weird, "double trouble" episode where the star played his or her own twin cousin or something).

So Sarah Michelle Gellar can’t be blamed for floundering a bit in the CW's new thriller series Ringer, playing reformed wild child Bridget and her wealthy twin sister Siobhan — especially when Siobhan mysteriously disappears during a boating trip and Bridget conveniently takes over her life, unbeknownst to anyone else.

Need I mention that Bridget is a fugitive from witness protection and Siobhan has a dark past that may be even more dangerous?

This series also brings up the biggest challenge a TV critic faces. Film critics and theater critics only have to judge the work before them.

But analyzing Tv shows requires gauging the potential of a series pilot -- asking if producers and the stars build something compelling, even if the first episode is a bit lacking.

On that question -- which I often boil down to a simple TiVo or Ti-NO question -- I've decided Ringer's facing a high bar.

Originally developed for CBS, this show wastes some pretty cool actors (Lost alum Nestor Carbonell as a dogged FBI agent and Fantastic Four’s Ioan Gruffudd as Siobhan’s arch, wealthy husband, to name two).

Too adult for the CW but too lightweight for CBS, it’s a game effort in need of serious innovation.

In other words, Ti-NO.