The Daleks? Check. The Cybermen? Check.

The Tritovore ... who?

That's a question BBC hopes fans won't be asking come Easter when the next "Doctor Who" special is set to air with David Tennant and special guest companion Michelle Ryan.

The Tritovore are a new bad guy described by The Mirror as part man, part fly.

"They are disgusting and will last long in the memory," a source told the newspaper. "Everyone remembers the Daleks and the Cyberman, but not a lot else if their honest. The Tritovore will change that."

The Tritovore will be a part of an episode already billed "Planet of the Dead," and will bring Ryan -- best known to American audiences as the star of the short-lived NBC series "Bionic Woman" -- back to the small screen. It also will begin what will be the final stretch of episodes for Tennant, who announced late last year he would be leaving "Doctor Who," to be replaced by Matt Smith.

Little else is known about the episode, except from a publicity still that shows Tennant and Ryan in what appears to be the back of an older style bus.

Talk continues to swirl that either Ryan is the new full-time companion for when the fifth season begins in 2010, or that the specials slated to appear throughout 2009 are sort of an audition for full-time companions.

The inclusion of the Tritovore has not been confirmed by BBC, so it should be treated as any rumor would.

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