Before she joined WWE, Jillian worked the independent scene under the name Macaela Mercedes; acting as an arrogant heel. She joined OVW as Jillian Hall and started as a babyface until she bleached her hair and got breast implants, leading to an angle where the implants leaked into her brain and turned her into a psychotic villainess.
Jillian debuted on the main roster on July 28, 2005 as the villainous publicist to the MNM faction. Part of her gimmick included a grotesque "mole" on the left side of Jillian's face. She would go on to act as the publicist for John Bradshaw Layfield later in the year, and it was during that time that she engaged in a brief feud with Stacy Keibler. The feud led to Jillian's in-ring debut on Velocity, where she cheated to beat Stacy. During the match, the evil Jillian donned a mask to cover up her mole, which was later bitten off by The Boogeyman in January 2006. Jillian's alliance with JBL ended shortly after WrestleMania 22, as did her tenure as a villainess.
After spending the rest of 2006 as a babyface, Jillian turned into a villainess due to her jealousy of the attention that Ashley Massaro had been receiving. In her second stint as a heel, Jillian decided to show that she had more talents other than wrestling, so she would start singing...badly. This gimmick stuck with her for the rest of her time in WWE. Jillian would finally capture the Divas Championship by defeating Mickie James on October 12, 2009, but she lost the title to Melina just a few minutes later. Jillian left WWE in early 2010.
In her first run as a villainess, Jillian was conniving and calculating, as well as twisted and vicious. In her second run, Jillian was mostly comic relief.