Ashlee Simpson and Pete Wentz are urging guests attending their Saturday night wedding to dress dark for the nuptials. Approximately 150 guests will attend the top-secret event, according to reports - and those close to the couple have been told to expect a fantasy-themed ceremony and party.

One guest tells Us magazine, "We have been asked to wear cocktail attire, but to not be overdressed."

Neither Simpson nor Wentz have confirmed the wedding is taking place, but the couple enjoyed what appeared to be separate bachelor and bachelorette parties in Los Angeles on Thursday night.

A large tent has been erected in the backyard of the Simpson family compound in Encino, California.

Rumors of the big night have been running rampant since the beginning of May. The couple announced its engagement last month.

-Ashlee Simpson Pictures

(This news article provided by World Entertainment News Network)