Chris Brown explains the word 'disappear' and sings 'See the Signs' with Elmo (Note: Brown's song was pulled from broadcast due to his 2009 arrest).

Alton Brown explains 'recipe' with Abby Cadabby.

Drew Brees discusses the word 'measure' with Elmo.

Benjamin Bratt demonstrates 'translate' with Elmo.

Zach Braff discusses 'anxious' with Telly.Julie Bowen discusses 'binoculars' with Elmo.Andrea Bocelli sang a lullaby to Elmo based on the song 'Time to Say Goodbye'.James Blunt (singing about triangles in episode 4144).Emily Blunt as Arizona Emily defines the word 'explore' with Idaho Elmo.Jack Black discusses 'octagon' and 'disguise' with Elmo.BeyoncГ© (lead singer of Destiny's Child) sings 'A New Way to Walk'.Halle Berry presenting the word 'nibble' with Elmo.Candice Bergen lip-synced 'C is for cookie'.Richard Belzer both appeared on the show and they have a puppet that strongly resembles him.Kristen Bell defines the word 'splatter' with Elmo and Abby Cadabby.David Beckham acted out the word 'persistent' with Elmo.Jason Bateman discusses the word 'comfort' with Elmo.Tiki Barber defined 'quest' and helped sing 'Set Your Piggies Free'.Tyra Banks acted out the word 'struggle' and sang the alphabet song with Abby Cadabby (Note: This video was posted on YouTube, following the season finale).Carl Banks (one special): Banks, a New York Giants player, appeared during the celebrity performance of 'Put Down the Duckie' in Put Down the Duckie: The Sesame Street Special.Beetle Bailey appeared in a season 6 segment demonstrating 'under'.Backstreet Boys sang 'One Small Voice' with Elmo.Hank Azaria defines the word 'imposters' with Elmo.

Patricia Arquette defines the word 'metamorphosis' with Abby Cadabby.

Will Arnett appeared as Max the Magician in episode 4166.

Christina Applegate defines the word 'booth' with Elmo.

Carmelo Anthony defines the word 'compare' with Grover.

Aziz Ansari defines the word 'ridiculous' with Grover.

Kofi Annan helps Elmo and his friends sing the alphabet.

Buzz Aldrin NASA footage of Apollo 11 mission, episode 3697 explains to Cookie Monster that the moon is not a giant cookie, episode 4090.

Jessica Alba defines the word 'scrumptious'.

Casey Affleck demonstrates the word 'careful' with Murray.

Amy Adams defines 'ingredient' with Elmo.

Kareem Abdul-Jabbar defines the word 'subtraction' with Big Bird.

Talking alphabet elmo