Lost Casts Dexter Baddie as Mysterious "Man No. 1"

Mark Pellegrino, whom Dexter fans for certain will remember as Rita's hate-to-hate-him druggie/abusive husband, has been cast on ABC's Lost, sources confirm for TVGuide.com.

Pellegrino will likely make his first appearance in the two-hour Season 5 finale, airing May 13. His casting was first reported by EW's Ausiello.

Who is Pellegrino playing? "Officially," our source tells us, he is billed on the call sheet as "Man No. 1." That is obviously meant to be as generic as "Sexy Stewardess" - but perhaps more can be read into it, if one were (ahem) inclined. Ask yourself: Who is the BMOC in Lost-land?

Character name aside, Hawaii-based eyewitnesses tell the Dark UFO fansite that Pellegrino thus far has filmed a scene in which he is on hand for Locke's crippling fall from a window. The speculation is that Man No. 1 will also have a Zelig-like presence at other formative events in each castaway's pre-island life.

Who in Lost lore would be so omnipresent? Are you thinking what we're thinking?