Ready, set, snip. On the episode of “Buffy the Vampire Slayer” set to air Jan. 8, the show’s star, Sarah Michelle Gellar, is doing the unthinkable: She’s having her hair cut. The long blonde locks will be gone. The title of the episode? “Gone.” But will that produce some sort of Samson-and-Delilah effect on the currently strong ratings for “Buffy”? (When Delilah cut Samson’s hair, there went his power.) Well, the New York Post, citing the 30 percent ratings drop in 1999 when “Felicity” star Keri Russell lopped off her curls, suggests that producers of the UPN show forced Gellar, 24, to try out the new do as a wig — just in case. Yet it appears that she did lose a couple of inches of hair — which have grown back in the two months since the show was shot. “I think it looks like it was done with a weed-whacker,” the Post quotes one Internet news group’s reaction to Gellar’s photo with the shorter style. Silly as all this may sound, the reaction to Russell’s loss of curls prompted her network, the WB, to announce a prohibition on haircuts for their actors without express permission from the company chiefs, says the Post. And, sure enough, the ratings for “Felicity” grew back as Russell’s hair did.