We all have our vices -- Jessica Simpson is no different. Hers has an odd twist though, which puzzled Jay Leno on the 'Tonight Show' (weeknights, 11:35PM ET on NBC). She's addicted to Nicorette gum, but has never once smoked a cigarette.

Watch the video after the jump. We all have our vices -- Jessica Simpson is no different. Hers has an odd twist though, which puzzled Jay Leno on the 'Tonight Show' (weeknights, 11:35PM ET on NBC). She's addicted to Nicorette gum, but has never once smoked a cigarette.

Said Leno, "[That is] like, 'I'm on methadone. I've never done heroin; I just enjoy methadone.'" But Simpson further explained how the gum habit came about and her obsession with the "party in [her] mouth."