This is a big year for Sesame Street. Big Bird, Grover and the gang are celebrating their 39th season on PBS... and in hi-definition no less. The award-winning preschool series premiered on Monday with some cool new learning concepts. The show is merging mathematical reasoning and language skills to help kids talk about how to solve problems (instead of just thinking 1+1=2). Leela, a new cast member from India, moves to Sesame Street and starts introducing her heritage and culture with her new friends. And after a successful start last year, Word on the Street, an outdoor segment filmed in NYC, returns to introduce new words in rich and meaningful contexts.

Fortunately, Sesame Workshop has recruited plenty of help. Among this year's A-list celebrities: Will Arnett (with some magical math), Jessica Alba, David Beckham, Brian Williams (with an update about sharing), Jenny McCarthy, LL Cool J (rapping with Elmo), Neil Patrick Harris (as the Shoe Fairy?), Sandra Oh, Heidi Klum, Jack Black (who is looking for octagons), Megan Mullally, and Jonah Hill.

Not enough? How about the new parodies: Preschool Musical (singing, dancing three-year-olds), 30 Rocks, the Plain White Tees (yup, they're actually teeshirts), and Dirtiest Jobs (with Mike Rowe and Oscar the Grouch of course), and a winning performance of Feist's 1234 ("1 2 3 4 chickens just back from the shore"). If last season's highlights are any indication, it's going to be a great season:

• Tina Fey as a pirate
• Anderson Cooper for the Grouch News Network
• Sugarland singing with Elmo
• James Blunt and his lost triangle
• Rachael Ray sharing her favorite words
• Chris Brown seeing the signs

And to top it all, Sesame Workshop just launched a new website with their incredible archive of live-action Muppet videos. The site will introduce new educational themes every day, so there's no end to the learning. See you around the neighborhood!