“20/20” (9 p.m., ABC): “20/20” profiles Vegas showmen Siegfried and Roy as

“20/20” (9 p.m., ABC): “20/20” profiles Vegas showmen Siegfried and Roy as they prepare for what has been billed as their “farewell performance.” Included: An update on Roy’s recovery from the life-threatening injuries he suffered in 2003 when he was mauled by a tiger.

“Planet Forward” (online at planetforward.org): The broadcast conclusion to “Planet Forward” doesn’t air on PBS until April 15. But in the weeks leading up to this finale, the “Planet Forward” initiative is rejecting the topdown, experts-dominated model for public-affairs programming in favor of a bottom-up approach where citizens lead the conversation. With that in mind, “Planet Forward” will debut online Friday as a virtual town square, hosted by Emmy-winning journalist Frank Sesno.