When Phineas and Ferb find out that their grandma Betty Jo used to be a roller-derby queen, they build an awesome rink—right in their backyard! Soon they discover that Jeremy Johnson's grandmother used to be their Grandma's skating rival, so they set up a contest to see which granny can roller derby her way to the finish line the fastest. The thrills continue when Phineas and Ferb build a gorge so their grandpa can do a radical stunt jump over it!...

After finding out that both their grandmother and Jeremy Johnson's grandma used to be skating champs, Phineas and Ferb build an awesome rink right in their backyard, and they set up a contest to see which granny can roller derby their way to the finish line the fastest.