[1] Since June 2015, she has been the Head of Storytelling for the entire My Little Pony and Littlest Pet Shop brands, helping to "create expansive worlds and characters".
In October 2010, she was invited by Lauren Faust, the co-creator and producer for Foster's Home for Imaginary Friends, to help write on Hasbro's television revival of its My Little Pony franchise.
McCarthy, on a writing hiatus at the time, was inspired to accept by Faust's dedication and the strong female characterization she had presented.
[1] In addition, McCarthy has written and helped produce the spin-off films, My Little Pony: Equestria Girls and its sequel.
She was nominated for a Daytime Emmy for "Outstanding Original Song - Children's and Animation" for her lyrics in the Friendship Is Magic episode "Sweet and Elite".