'Smallville' goes back for its final go-round

Expect more than one blast from the past as "Smallville" begins its 10th and final season Friday.

"Our theme this year is really Clark exploring the ghosts of his past so he can move on," says Brian Peterson, executive producer of the series.

For years, Clark Kent (Tom Welling) has moved ever closer to his role as Superman -- and to the love of his life, Lois Lane (Erica Durance). As that future beckons, one star making a return appearance is John Schneider, who played Pa Kent; his character died in Season 5.

"He returns in a very emotional scene," said Peterson's fellow executive producer, Kelly Souders. "I just watched it cut together for the first time the other day and it made me get up, cross the room and get a Kleenex, actually. And I don't cry very easily. But it's really moving to see both of those actors and both of those characters on-screen together again."

Pa Kent isn't the only father figure making a return appearance. Also look for John Glover, as Lex Luthor's dad, Lionel, to come back.

"We have him for at least two episodes, but hopefully more," Peterson said.

Laura Vandervoort, who played Clark's Kryptonian cousin Kara, also will return.

In doubt is the return of two stars who were central to the series for several seasons: Kristen Kreuk as Lana Lang and Michael Rosenbaum as Lex Luthor. They left as cast regulars at the end of Season 7.

"We would love to have them back, and literally that's all we can say," Peterson said. "It's not in our court; we have done everything in our power to get them back."

Amid all the returns, one longtime character is exiting. Allison Mack, who plays Clark's friend Chloe Sullivan, is leaving the cast. She's the only remaining star other than Welling who has been with the show since the beginning.

"She'll be in the premiere, then back again around midseason and, hopefully, toward the end of the season," Souders said.