|Premiere||November 10, 2009 (4187)|
|Finale||February 18, 2010 (4212)|
Sesame Street Season 40 premiered on November 10, 2009. This date is the 40th anniversary of the show, and Sesame Workshop celebrated the occasion with a commemorative book and DVD set, as well as a week-long takeover of the Google logo.
The curriculum for Season 40 focuses on environmentalism and is "designed to nurture young children's appreciation and love for nature."  The Muppets of Sesame Street encourage children to explore their curiosity in the outdoors with activities that teach simple, age-appropriate ways of showing care and stewardship for the environment. Several episodes focus on environmental issues - such as recycling or habitats. One episode (Episode 4193) focuses on Baby Bear and his family learning how to hibernate. Another episode (#4187, originally planned as #4210) features Big Bird learning about migration.
A new computer-generated segment, Abby's Flying Fairy School, was added this season. Murray Has a Little Lamb and Bert and Ernie's Great Adventures return from last season and alternated with each episode. What's the Word on the Street and The Word of the Day also return with 26 new words. Elmo's World returned for its eleventh season with only one new segment about Frogs.
Parodies included "Mad Men" (based on Mad Men), "Waiting for Big" (Sex and the City), "Outdoors" (based on "I'm Yours"), "Super K Cereal" (based on Special K), and "D-Dance" (based on Apple's iPod commercial).
- What's the Word on the Street? (30 seconds)
- Sesame Street Theme (50 seconds)
- Street Story (10 to 12 minutes)
- Celebrity Vocabulary Word (1 minute)
- Murray Tune-In (1 minute)
- Letter film (1:15)
- Abby's Flying Fairy School (8:30)
- Murray Tune-In (1 minute)
- Number film (1:15)
- Bert and Ernie's Great Adventures or Murray Has a Little Lamb (5 minutes to 6:30)
- Murray Tune-In (1 minute)
- Music video or curriculum spot (2:15)
- Elmo's World (17 minutes)
- Murray close (30 seconds)
- End credits (45 seconds) 
The change in format and curriculum increased viewership (compared to February 2009 ratings) by 60%.
Episodes 4187 - 4212 (26 episodes)
- Episode 4187 - Big Bird considers moving
- Episode 4188 - The Cowmonster Pair
- Episode 4189 - Abby turns Chris and Baby Bear into bees
- Episode 4190 - Wild Nature Survival Guy on Sesame Street
- Episode 4191 - Abby makes seasons change
- Episode 4192 - Y a Quest? Y Not
- Episode 4193 - Bears try to Hibernate
- Episode 4194 - Stinky's annual birthday flower
- Episode 4195 - Elmo finds a baby bird
- Episode 4196 - Grouch Messing Machine
- Episode 4197 - The Cookie Tree
- Episode 4198 - Mary Mary Quite Contrary makes a garden
- Episode 4199 - Abby gets the Sparkle Speckle Fairy Freckles
- Episode 4200 - The Rainbow Show
- Episode 4201 - Amphibian Show
- Episode 4202 - Chris and Elmo go camping
- Episode 4203 - Squirmadega car race
- Episode 4204 - Jack's big jump
- Episode 4205 - Inspected by 4
- Episode 4206 - Big Bird sprains his wing
- Episode 4207 - The Planet G
- Episode 4208 - The Counting Booth
- Episode 4209 - Tribute to Number Seven
- Episode 4210 - Abby's tricycle
- Episode 4211 - Jack grows his own beanstalk
- Episode 4212 - The Prince and the Penguin
Murray, Elmo, Abby Cadabby, Telly, Baby Bear, Rosita, Zoe, Big Bird, Snuffy, The Count, Oscar, Grover, Curly Bear, Papa Bear, Mama Bear, Forgetful Jones, Kermit the Frog, Ernie, Bert, Stinky the Stinkweed, Horatio the Elephant, Slimey, Little Bo Peep, Wolfgang the Seal, Harvey Kneeslapper, Grundgetta, Sherlock Hemlock, Jack Be Nimble, Biff, Sully, Mr. Johnson, Herry Monster
- Season 40 introduces a new opening and closing theme sequence.
- Starting this season Joey Mazzarino is the new head writer.
- This was Mike Renzi's last season as the show's music director.
- In an interview with Muppet fansite Tough Pigs, writer and Muppeteer Joey Mazzarino said, "We're trying to do what we call a hidden gem in every episode. That's for you guys, the fans. Little things like Biff and Sully in a scene, or some other stuff that I won't tell you about that will be hidden in the scene."
- A parody of Jon & Kate Plus 8 featuring The Count and Anything Muppet spoofs of the family was filmed for this season, but never made it to air (most likely due to the couple's splitting up). A plot outline of the sketch was also removed from the Season 40 Press Kit "Parody Description" section. The segment was released as a bonus feature on the Best of Sesame Street Spoofs! DVD in 2011.
- Select episodes from this season can be purchased in The iTunes Store.
- This is the first season to not have any clips featuring any characters performed by Jim Henson.
- Kermit the Frog makes a surprise cameo on Elmo's World: Frogs.
- Maria: Sonia Manzano
- Alan: Alan Muraoka
- Gordon: Roscoe Orman
- Gina: Alison Bartlett
- Luis: Emilio Delgado
- Bob: Bob McGrath
- Susan: Loretta Long
- Gabi: Desiree Casado
- Chris: Chris Knowings
- Leela: Nitya Vidyasagar
- Caroll Spinney as Big Bird and Oscar
- Pam Arciero, Jennifer Barnhart, Fran Brill, Tyler Bunch, Leslie Carrara-Rudolph, Kevin Clash, Bruce Connelly, Stephanie D'Abruzzo, Eric Jacobson, John Kennedy, Tim Lagasse, Peter Linz, Jim Martin, Joey Mazzarino, Paul McGinnis, Jerry Nelson, Carmen Osbahr, Frank Oz, Martin P. Robinson, David Rudman, Matt Vogel, Steve Whitmire, Bryant Young
- Executive Producer: Carol-Lynn Parente
- Coordinating Producer: April Chadderdon
- Senior Producer: Tim Carter
- Line Producer: Stephanie Longardo
- Producers: Melissa Dino, Benjamin Lehmann, Ronda Music Lask
- Directors: Kevin Clash, Ken Diego, Jim Martin, Ted May, Joey Mazzarino, Scott Preston, Millicent Shelton, Lisa Simon, Matt Vogel, Nadine Zylstra
- Head Writer: Joey Mazzarino
- Writers: Molly Boylan, Annie Evans, Christine Ferraro, Judy Freudberg, Tony Geiss, J Milligan, Emily Perl Kingsley, Luis Santeiro, Ed Valentine, Belinda Ward, John Weidman
- Head Writer (Elmo's World): Judy Freudberg
- Co-Executive Producer (Elmo's World): Kevin Clash
- Production Designers: Victor DiNapoli, Bob Phillips
- Project Director (Abby's Flying Fairy School): Christine Walters
- Additional Voices For Abby’s Flying Fairy School: Jeremy Redleaf, Jessica Stone
- Abby's Flying Fairy School characters designed by: Peter de Seve
- Puppets, Costumes, Props: Jason Weber with Connie Peterson, Rollie Krewson, Polly Smith, Andrea Detwiler, Michelle Hickey, Anney McKilligan, Lara MacLean, Chelsea Carter, Molly Light, Marc Borders
- Music Director: Mike Renzi
- Studio Music Director: Paul Rudolph
- Director of Music Operations: Danny Epstein
- Music Coordinator: Vicki Levy
- Composers: Tony Geiss, Ricky Gervais, Eric Perlmutter, Mark Radice, Kathryn Raio, Joe Raposo, JP Rende, Mike Renzi, Paul Rudolph, Bill Sherman, Russell Velazquez
- Costume Designers: Bill Kellard, Terry Roberson
- Art Director: Bob Phillips
- Prop Coordinator: Keith Olsen
- Art Direction/Graphics: Rickey Boyd, Pete Ortiz
- Sound Effects Editor/Re-Recording Mixer: Dick Maitland, C.A.S.
- Technical Director: Tom Guadarrama
- Cameras: Frank Biondo, Jerry Cancel, Shaun Harkins
- Vice President of Education and Research: Rosemarie T. Truglio, Ph.D.
- Special Thanks To: Creative Bubble, Celefex, Hyperactive Pictures, Misseri Studio, Speakeasy FX, Trollback + Company
- Taped at Kaufman Astoria Studios in New York
- ↑ 1.0 1.1 National Forum on Children & Nature: Sesame Street: "Connecting Preschoolers With Nature".
- ↑ Sesame Street gets local children’s perspectives
- ↑ Twardzik, Cathleen. Who is the fellow that's fluffy and yellow?. February 22, 2009
- ↑ Sesame Street at 40: A Night of Celebration with the Legendary Cast - Educators' Panel
- ↑ Joey Mazzarino interview
- ↑ Sesame Press Kit - Press Release
- ↑ Sesame Street: A Celebration - 40 Years of Life on the Street, page 167
- ↑ Sesame Workshop: Changes to Sesame Street’s 40th Season Prompt Major Ratings Increases
- ↑ Joey Mazzarino, Tough Pigs Interview with Joey Mazzarino
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