From Homestar Runner Wiki
Jackie Chapman is the wife of Matt Chapman. She gave birth to their first child in the summer of 2007, which was announced in a special Main Page message, and their second child in the fall of 2009, which was announced in a special entry on the FeedBurner page.
She helped write the script for the unreleased toon Tis True, Pom Pom, Tis True and played the Baby Lady in Peasant's Quest Movie Trailer. She also provided voices for an announcer in the Strong Bad Email theme song and a member of Advantage in The Limozeen Advantage. She was confirmed to be the "Scarfgirl" in secret identity.
The Brothers Chaps mention that during filming of the movie trailer, she was disgusted with her performance and made a sour face before her lines were over. This was proved true with the release of Peasant's Quest Outtakes on the Everything Else, Volume 1 DVD.