addition of a female character
I personally asked Bob Boyle why Daizy was added to the program. He told me it was because network execs asked that the show be made more female-friendly.
Aside from Go, Diego, Go!, I can't think of a single kids cartoon that has a predominantly female demographic that added a boy character to make it a more male-friendly show.
Ironic since most adult fans of My little Pony are men.