WHEREVER Paris Hilton goes, trouble follows.

And when the vixenish hotel heiress shows up this week on “The O.C.” to lay a big wet kiss on Seth Cohen (Adam Brody), it’s Seth’s girlfriend, Summer (Rachel Bilson), who seethes with jealousy.

Turnaround is fair play, however, as Summer gets distracted by a young actor, Grady Bridges (guest-star Colin Hanks, son of Tom), who has invited the whole gang to his birthday party.

And it wouldn’t be a party without the fun-loving Paris, who has been livening up prime-time this season with her reality show, “The Simple Life” (which just started production on a second season), and guest-starring stints on “Saturday Night Live,” “ABC’s “George Lopez” and NBC’s “Las Vegas.”

Elsewhere on the red-hot “O.C.,” Ryan (Benjamin McKenzie) struggles to prevent Marissa (Mischa Barton) from learning a devastating secret about her ex-boyfriend, Luke (Chris Carmack) -he’s having a steamy affair with Marissa’s sexy mom, Julie (Melinda Clarke).

THE O.C.

Wednesday, 9 p.m., Fox