Are wedding bells in store for Sarah Chalke and Josh Radnor's characters on "How I Met Your Mother"? And if so, does that make Stella (Chalke) the "mother" of Ted's (Radnor) children? ET goes behind the scenes with the stars of CBS' hit comedy to get to the bottom of these big mysteries!

"Ted and Stella are gettin' hitched," says Neil Patrick Harris (a.k.a. ladies' man Barney) with his signature dry humor. "Ted and Stella and are definitely getting married."

"There are weddin' bells a ringin' on Stage 22," teases Cobie Smulders, who plays Ted's ex Robin on the show.

On this week's episode of "HIMYM," the gang attends the wedding of Ted and his new girlfriend Stella. Hilarity ensues when the always deviant Barney decides he wants another go around with Robin, who is making the wedding increasingly awkward with her constant references to her old bed shakin' good times with Ted. But is everything as it seems?

"How do you know [the wedding scene] was real?" Radnor says. "We do a lot of fantasy sequences on 'How I Met Your Mother.'"

As to the other big question of whether or not Robin is the "mother" of Ted's children, Smulders says of her character: "I've sort of given up on me being the mother. I dont think I am. With our show. ... I don't even know what we are shooting next week so I ... have no idea how this story is going to end."

Tune into this week's episode of "How I Met Your Mother" Monday night, Oct. 20 to find out another piece in the mystery!