It’s a special time of year on Wisteria Lane. The Christmas ornaments are up, the housewives are outside decorating a community tree – and disaster is looming.

“Oh crap, who’s dead now?” says an exasperated Susan (Teri Hatcher), sensing yet another casualty when she sees an ambulance down the street.

That’s not even Sunday’s big event, but it might serve as a slogan for Desperate Housewives‘ (9 p.m. ET/PT) seemingly annual mayhem. Over the years, the street and its residents have endured a tornado, a hostage-taking and fires, not to mention numerous deaths.

This time, it’s a plane carrying a banner – Karl’s marriage proposal to the cheating Bree (Marcia Cross) – that crashes the neighborhood’s holiday festival.

“The very end of the episode has dire ramifications for everyone on Wisteria Lane,” creator Marc Cherry says. “There are three deaths. One is a character the audience has never met, one is a minor character on the street and one is a character who we introduced in the very first season, a big player.”

It’s the first time Housewives has had its disaster at Christmastime. Despite the death toll, Cherry says the crash episode will have more comic elements than its destructive predecessors.

The story “seems incredibly huge and funny and tragic all at the same time, which is quintessential Desperate Housewives,” says Cross, pleased that the prim Bree is getting to show “her primal side” this season.

If Wisteria Lane seems like a disaster area, it’s part of the show’s heightened reality, says Felicity Huffman, who plays Lynette.

“I think Marc came up with a great formula, which is all the kind of crazy wickedness that goes on, with a dash of mystery. So with mystery comes danger, and with danger often comes death,” says Huffman, whose character’s pregnancy has complicated home, work and social relationships.

The tree-trimming scene, which features perfectionist Bree laying tinsel perfectly while the less-precise Gabrielle (Eva Longoria Parker) is flinging it in clumps, marks an infrequent gathering of the original housewives, who are often apart on their own story lines.Gabrielle is mad at Lynette, who sued Gabrielle’s husband, Carlos. Bree, preoccupied with her extramarital affair, is finally made aware of Lynette’s pregnancy. And Susan, who has had her hands full with the increasingly mad Katherine (Dana Delany), is trying to keep the peace. (The ambulance has to do with Katherine’s stabbing last week.)

The Gabrielle-Lynette battle “is going to climax in this episode,” Longoria Parker says. Afterward, “they could be friends. Or not. Or one could be dead.”

Cherry says the crash will affect almost every relationship, including Gabrielle and Lynette’s friendship, Lynette and Tom’s marriage and the Karl-Bree-Orson triangle. It will cause the street’s residents to consider their past lives as they fantasize about the future.Housewives (15.2 million viewers) is down 2 million this season but remains a strong ratings performer, ranking 10th in viewers and fifth in the advertiser-coveted 18-to-49 demographic.

Cherry recently signed a development deal that could extend Housewives two years beyond the seven initially planned. The actresses, who would have to negotiate new deals, all say they would like to stay until the end, although Huffman has concerns if Cherry becomes too busy with other projects to contribute his unique voice.

“I’m here for the long haul,” Hatcher says. “I’ve always said that I’m here until I’m the casualty of one of these disasters – which will not be at my request.”