Cathy Simms, played by Lindsey Broad, was Pam Halpert's temporary replacement while she was on maternity leave. During her employment, she developed a friendship with Jim Halpert, and despite his marital status, she planned to seduce him.
Biography
Little is known of Cathy's life before her time at Dunder Mifflin, although in a deleted scene she mentions a rich man who had offered to marry her.
Season 8
In "After Hours", Cathy entered Jim's Hotel room saying that the heating in her room wasn't working, but her true intention was to seduce him. Jim realized what she was doing after she took a shower in his room and came out in a bathrobe, and then got under the sheets in only her lingerie. Jim called Dwight for help, under the pretense of there being bedbugs in the room. Dwight chased her out by spraying "a compound of chemicals" into the sheets, and then on Cathy after Jim kept pointing to her shouting that he saw bugs. Dwight successfully (and unknowingly) chased her out, and then told Jim he couldn't stay in the room because of the chemicals, and suggested he bunk with Cathy. She is never mentioned after Last Day in Florida.