Brian allowed Stewie to talk him into resisting sex with Carolyn until she finally left him for Cleveland, believing that Brian only wanted friendship.
When Cleveland considered marrying Carolyn, Cleveland's ex-wife Loretta Brown asked him to come back to her but he turned her down.
Cleveland returned to find Carolyn was cheating on him with Quagmire. Cleveland later found out that she gave him genital warts.
In "Valentine's Day in Quahog", Stewie gathers scores of Brian’s former girlfriends including Carolyn to get to the bottom of why he’s unsuccessful in love.
She was the voiced by Kat Foster and used to be a love interest of Brian Griffin until she dated Cleveland and then Quagmire.