Jennessa's first voice-over role at 6 years old was in Disney's "American Dog", directed by
Chris Sanders, whom she worked with many times throughout production. The film was scheduled for release in 2007. The protagonist of the film was a canine actor, Henry, who starred in his own show as a secret agent. While filming a show, one of the stunts went wrong and Henry blacked out and found himself stranded in the Nevada desert, 2,000 miles away from home. Henry must make some new friends, including a one-eyed cat and a giant, radioactive rabbit and a little girl.
Ultimately, the movie was considered too surreal and "too bold". Sanders was later replaced with
Chris Williams and
Byron Howard, and the movie was soon thereafter reworked into
Bolt (2008), which was released in 2008, with a new cast, with Jennessa herself being replaced with
Miley Cyrus.