Flo Jerkins is both Madame Foster's arch rival and good friend. She is the main antagonist of The Big Leblooski, but makes a few more appearances throughout the series as a friend rather than a for to Madame Foster.
Flo Jerkins is an elderly woman with large, poofy pink hair and pointy glasses who speaks with a heavy southern accent.
Flo has been Madame Foster's arch nemesis ever since they were kids. In The Big Leblooski, Flo bribes all the members of Madame Foster's bowling team to join her team instead by knitting doilies. Mac, Wilt, Eduardo, and Coco decide to join her team before the bowling tournament. Everyone on Madame Foster's team prove to be great bowlers except for Mac, who had never bowled a day in his life. Madame Foster then discovers Bloo's talent and decides to replace Mac.
With Bloo on her team, Madame Foster began to take the lead, leaving Jerkins' team in the dust. Towards the end of the tournament, Jerkins bribes Bloo into joining her team using the paddle ball that he'd been trying to get out of the claw machine. It was the final round, and Madame Foster needed a replacement for Bloo. Mac, who had been taking bowling lessons from an imaginary friend named Bowling Paul, asks to rejoin the team in Bloo's stead. Desperate, Madame Foster allows him to join. Amazingly, Mac bowls a strike, declaring Madame Foster's team the winner.
After the tournament, Flo and Madame Foster make plans to have tea. When Mac asks why they're making plans if they hated each other, and Madame Foster states that "just because they're arch rivals doesn't mean they can't act civilized now and again."
Flo makes another appearance in Foster's Goes to Europe. Madame Foster was going to throw a wild tea party while Frankie and the others were in Europe. However, Flo and the rest of Madame Foster's friends end up showing up to Foster's before everyone else left, and Frankie found out about the whole thing and realized that Madame Foster couldn't be trusted while they were gone. Later that episode, Madame Foster takes Flo and the rest of her friends (and Eurotrish) to Europe using the plane tickets that she stole from Mac.
Flo appears again in Say It Isn't Sew. Madame Foster and Bloo are just about to leave the fabric store to go to the amusement park when she bumps into Flo and they decide to stay longer and make doilies, much to Bloo's dismay.
Flo makes her final appearance in Goodbye to Bloo. Bloo convinces Flo and a bunch of her other motorcycling buddies to perform a trick that involved them riding their motorcycles up a ramp that he built and over the Foster's swimming pool with an imaginary shark in it, in exchange for solid gold bars. Just then, Madame Foster calls her to tell her there's a huge party inside the house, and they all leave Bloo behind to join the party.