Mary Lou Milligan is a character in the first episode of Happy Days. She was once a love interest of Richie Cunningham until the episode's ending. Despite that, she will join Richie and his friend in some of the various Winnie the Pooh crossovers and some Land Before Time crossovers.
- Ralph met Winnie the Pooh, Ash Ketchum, SpongeBob SquarePants, and their friends on Pooh's Adventures of Happy Days.
- Ralph will meet Littlefoot, Bloom, and their friends in the first episode of Littlefoot's Adventures of Happy Days.
- Ralph will meet Aladar and his family in Littlefoot's Adventures of Dinosaur.