The return of Thelma the unicorn

Told in rhyming text, Thelma is a pony who created a big splash when she dressed up and posed as a unicorn, but she returned to her best friend Otis the donkey when fame proved to be stressful; now her many fans want her back, and Thelma is reluctant--until Otis agrees to go along as her manager and backup, so she can concentrate on being awesome.