WHAT'S ON TODAY.

9 P.M. (ABC) SIEGFRIED & ROY: THE MAGIC RETURNS ''20/20'' travels to Las Vegas to witness a one-night-only performance by the animal illusionists Siegfried & Roy, featuring Montecore -- the 380-pound Bengal tiger that mauled Roy Horn, in October 2003 -- as part of a Power of Love gala benefiting the Lou Ruvo Brain Institute. Elizabeth Vargas (above, with Siegfried, right, and Roy) interviews the two men at their home, where they speak about their career and Mr. Horn's recovery before making their appearance at the Bellagio Hotel and Casino, which was taped on Saturday. 10 A.M. (55); 3 P.M. (NBC) THE ELLEN DeGENERES SHOW Will this never end? Jason Mesnick of ''The Bachelor'' infamy talks about his do-over with Molly Malaney, who reveals what made her take him back. [ABSTRACT FROM PUBLISHER]