Who Can Wear the Most Hats on Their Head" Day comes but once a year, and Elmo and Zoe are ready for some serious sombrero stacking! Abby Cadabby helps out with magic while The Count counts along. Who will win? Plus: David Beckham teaches Elmo about the word persistent," and in 30 Rocks," Liz Lemon and Jack the Boss count 30 rocks for their show. Brought to you by the letter U and the number 14.