Bitsy Hannigan is the mother of Mike Hannigan. Her husband is Theodore Hannigan. Bitsy and Theodore dislike Mike's new girlfriend Phoebe Buffay and they try to get him to go out with somebody else. But, Mike tells Bisty and Theodore that he loves Phoebe and Phoebe tells Bitsy that she threw up in the closet!
At Mike and Phoebe's engagement party, Monica makes Phoebe look like a fool in front of Theodore and Bitsy so Phoebe shouts at Monica.
Theodore and Bitsy's final appearance was at Mike and Phoebe's wedding, in "The One With Phoebe's Wedding".