Susanna Ivonna "Susie" Carmichael is one of the main character from Rugrats, All Grown Up! and Angelica and Susie's Pre-School Daze. When Susie sang at Didi's baby shower in the first movie, it was the first time that she displayed her talent for singing, a talent that would later become the most important part of her character.
But in 2003, when the spin-off All Grown Up! was put into production, a press release for the show announced that "smart, spunky Susie (Cree Summer), still a crusader for what's right, and upstages Angelica as a singer with real talent", which implied an increased role for Susie in the new spin-off. Besides her singing talent, it was revealed that she also knows ten languages, as shown in the episode "Runaround Susie".
The very first episode of the regular run, "Susie Sings The Blues" (first US tx: November 29, 2003), concerned Susie and her singing talent. Since then, she has appeared in a majority of the episodes (although still in less than the other characters). This may be explained by the fact that by the time All Grown Up! premiered, Summer had less regular roles on other shows. Also, while Susie and Angelica still treat each other as rivals (especially at singing, see "Susie Sings The Blues" and "It's Karma, Dude!" for cases in point), the two actually hang out with each other. Angelica has become jealous of Susie's singing and tomboyish beauty. On the other token, Susie has become somewhat of a "best" friend to Angelica. Susie helps Angelica find her doll in "Saving Cynthia".