This full-length episode includes popular segments such as Elmo’s World, Letter of the Day, Number of the Day and Global Grover. Will Rocco the Rock float? Will a leaf sink? Join Elmo, Zoe, Telly, and Gordon as they test out hypotheses with experiments about floating, sinking, and sliding. This complete episode also focuses on sign language and physical movement. Ernie delivers a Forest Fashion report, Global Grover returns from Nicaragua to explain how bricks are made, and an observant gardener lends a hand to some "Desperate Houseplants." This episode is brought to you by the letter P and the number 15.