Susan is revealed to be a vegetarian in "The One With The Dozen Lasagnas". She works in advertising.
Susan and Carol had an affair while Carol was married to Ross. Ross and Susan have never gotten along very well, mainly because Ross resented Susan for "stealing" Carol away from him. Susan resented Ross for his romantic history with Carol as well as his awkward behavior around her. During Carol's labor in "The One With The Birth", Ross and Susan even manage to compete in who fetches Carol some ice chips, resulting in Carol banishing them both from the delivery room. In "The One With The Sonogram At The End", they want to give Ross and Carol's unborn child the surname Willick-Bunch, excluding Ross from the title.
Susan's father appears to be in the military and both her parents seem very supportive and accepting of her relationship with Carol, specifically stating that while there is a Mother's Day, following her wedding to Carol.
Carol and Susan celebrated their anniversary together (although not the wedding anniversary) in "The One Without The Ski Trip".
Her final appearance was in the alternate reality episode of Season 6 where it is implied that no matter what Ross and Carol would not end up together. The mothers, Carol and Susan, are still together today in many other episodes and stories.
- "The One With The Sonogram At The End" (First appearance)
- "The One Where Underdog Gets Away"
- "The One With The Dozen Lasagnas"
- "The One With The Candy Hearts"
- "The One With Two Parts, Part 1"
- "The One With The Birth"
- "The One With The Breast Milk"
- "The One With The Lesbian Wedding"
- "The One Where Old Yeller Dies
- "The One With The Metaphorical Tunnel"
- "The One Without The Ski Trip" (Mentioned only)
- "The One With Rachel's New Dress"
- "The One Where Phoebe Hates PBS" (Mentioned in cut version/appears in uncut version)
- "The One That Could Have Been, Part 2"
- "The One With Rachel's Date" (Mentioned only)
- "The One With Monica's Boots" (Mentioned only)