Girlish Pigtails

Anime & Manga

 * Mikan from Alice Academy. Then again, she is still a very young girl.
 * The title character of Witch Hunter Robin has a really weird variation. Probably supposed to remind us that she's fifteen.

Western Animation

 * Gretchen from Camp Lakebottom has these, although they're probably meant to be ironic since she's a cynical Deadpan Snarker.
 * Lana Loud of The Loud House has two long braided pigtails, while her twin sister Lola wears her hair down.
 * Bubbles of The Powerpuff Girls. While all the girls are the same age, Bubbles acts the youngest.
 * Both Spinelli and Gretchen of Recess wear pigtails, though neither one falls under the standard "girly" or "childish" archetypes: Gretchen is The Smart Guy, while Spinelli is a Cute Bruiser Tomboy, though she is (month wise) the youngest of the gang.
 * Both Katie and Sadie of Total Drama, fitting their childish personalities.
 * Kitty in Total Drama Presents: The Ridonculous Race to signify that she's the younger and more carefree sister comparated to oldier sister Emma.
 * Kimiko Tohomiko of Xiaolin Showdown sports this as her default hairstyle when not in Expository Hairstyle Change mode.