Alumni from Buffy the Vampire Slayer and Bent add variables to The Big Bang Theory’s romantic equations.

Two new faces will join the cast of The Big Bang Theory during the show’s sixth season. TV Line reports that Ken Lerner (Buffy the Vampire Slayer) has been cast as Dr. Schneider, a dentist who begins a sly romance with the booming off-screen presence of Howard’s mother.

The principal cast will also face romantic complications. Margo Harshman – previously of Bent and Modern Family – will appear in several episodes as Sheldon’s new assistant Alex, who reportedly develops an interest in Leonard soon after meeting him.

Romantic insecurity seems to be a theme in the upcoming season. Howard’s discovery of Mrs. Wolowitz’s clandestine relationship is sure to be met with Howard’s signature lack of grace, while executive producer Steve Molaro indicates that Alex’s interest may inspire a little tension in Leonard and Penny’s romance. As of last season, the pair had rekindled their on-again, off-again relationship.

Molaro also hints that Sheldon and Amy Farrah Fowler will face romantic challenges as well, as Amy tries to coax a “reluctant” Sheldon down the road to a serious relationship. And none other than perpetually lonely Raj may be finding “a friend… very soon,” adding even more potential for hilarity and conflict in pursuit of love.

Though tensions are high among the characters, fans of the show don’t have much longer to wait. The Big Bang Theory season 6 premiers on CBS Sept. 27 at 8 p.m. EST.