It’s tricyclers versus triceratops in Sesame Street’s latest direct-to-DVD title. Elmo hosts this sharp, 40-minute show that introduces kids to scaly legends — explaining where they lived, what they ate — and even transforms Elmo, Telly, and Abby into extinct tap dancers for the almost too catchy song-and-dance number called “Doing the Dinosaur.” Twice as expansive as the slightly spotty Elmo’s World: Opposites and with a tighter script than the Elmo’s World: Pets, it's a must-see ... if you’re under 4.