BEVERLY HILLS, Calif. - Actors often talk about the oddity of being introduced for the first time to someone on a set and then immediately thrown into some passionate scene in a bedroom or a kitchen. Nathan Fillion says he can top that.

The Edmonton-native has just been cast as a gynecologist on "Desperate Housewives" (returning in September to CTV).

Fillion's first scene found him examining housewife heroine Susan Mayer, played by Teri Hatcher. "Hello Nathan, welcome to the show," is how Fillion remembers his first day on the job. "Put on this doctor's outfit. This is Teri. Teri, take off your clothes - and go."

That's exactly what happened, said Hatcher. "Hi, nice to meet you. Now, I'll get into these stirrups. Pretend you're doing some sort of exam nobody wants to talk about!"

Fillion praised Hatcher for making him feel so welcome on the set. "Well, that's pretty welcoming!" agreed Hatcher. "Hey, welcome to 'Desperate Housewives'!"

Hatcher and Fillion were still laughing about it at last Thursday night's ABC party which closed out the semi-annual network press tour. They were joined at the star-studded affair by "Desperate Housewives" creator Marc Cherry, James Denton (who plays former hitman Mike Delfino) and the actress who will play Fillion's wife on the series, Dana Delany.

Fillion and Delany play a married couple who move back to Wisteria Lane. Naturally, they share a deep, dark secret.

Delany's real-life secret is that she turned down the chance to play Bree Van De Kamp (the part that went to Marcia Cross) when the series was first launched in 2004. "You only get second chances two times in life," said Delany, who, when Cherry called again, was only too happy to pair up with Fillion. The two co-starred a few years ago on the short-lived but memorable drama "Pasadena."

Fillion caught Cherry's eye after starring as the skipper of the short-lived Joss Whedon sci-fi series "Firefly." (He was also just in the even shorter-lived Fox series "Drive.")

But back to that first scene. Why was Susan at the gynecologist's office? Rumours are starting to swirl about the fourth season of "Desperate Housewives," including whispers that Susan might be pregnant.

"There's going to be a big development at the end of the first episode of the season for her," is all Cherry would admit.

The producer has become an expert at dropping just enough hints at these press tour sessions to keep reporters hooked. The biggest bombshell apparently involves town tramp Edie (Nicollette Sheridan). "We've done something unusual with Edie," said Cherry. "I'm not going to say more than that."

Another storyline involves Lynette (Felicity Huffman) coping with chemo and cancer and the effect all of that is having on her family. The reason why Bree (Cross) is keeping her pregnancy a secret is revealed, plus Gabriella (Eva Longoria) and Carlos (Ricardo Antonio Chavira) continue to misbehave.

Cherry says he and the other writers have been going "through stories like nobody's business" in an effort to ramp up season four. "I tried to slow down in season two and I found out I had established a pace in season one that people liked," he said.

It's all part of serving what Cherry called "the beast that is television." As he put it, "Shakespeare only had to come up with about 44 hours of good material. We've already done 70 episodes."