Mama Van Koopa is one of the most wonderful koopalings in the games. Although she did not appear very often she is one of the most crucial characters in all of the games.
Super Mario Bros.
She is a hidden character in the first Mario Brothers game. On 8-4 fall in the third lava pool and see a hidden cutscene containing you and her enjoying the company.
Super Mario Bros. 3
She does not appear in this game but there are a few references about her. Mama Van Koopa is your mom in that reference.
Super Mario Bros. Wii
There is a hidden object on Super Mario Bros. Wii on 6-4. It looks kind of like a turtle. You press it and you automatically get subliminal messages that make you read fifty shades of grey. To see the rest of the Easter Egg, fall in the second lava pool. Mama Van Koopa will appear in the final level when you kill Bowser.