Imagine, for a moment, a world without “Sesame Street.” Young children would become less proficient spellers, counters and performers of musical odes to rubber duckies. Disposable diapers would be plain and void of images of Cookie Monster and Abby Cadabby. Elmo would cease to exist and, consequently, to be tickled.

Thankfully, this doomsday-for-children’s-programming scenario stands little chance of becoming reality. As “Sesame Street” celebrated the big 4-0 on Tuesday. Ernie, Bert and the rest of the gang have cemented their status as the most influential characters in American kiddie culture.

The “40 Years of Sunny Days” DVD set is hardly the first collection of previously televised “Sesame Street” segments to make its way to the marketplace, but this release is the first to provide a more complete look at the show, with footage that ranges from those early days in 1969 all the way to 2009.

Watching the evolution of pop culture on “Sesame Street” over those decades is perhaps this DVD’s greatest, giddy joy. In the ’70s, the attempts at currency and hipness translate into cameos from Henry “The Fonz” Winkler, C-3PO and R2D2 (who teach Big Bird to count), as well as at least one foray into funkiness courtesy of a Cookie Monster number titled “Me Lost Me Cookie at the Disco.” (Trust me, it’s kinda catchy).

The more recent clips bring appearances by Destiny’s Child, Neil Patrick Harris and Feist, and an iPod commercial riff that celebrates the letter “D” with footage of a dancing, day-glo Big Bird.

But the real genius of “Sesame Street” has never come from its guest stars or musical numbers. It lies in the show’s ability to talk to children on their level, without a hint of condescension or dishonesty, something that never shone through more clearly than in 1983, when all the adults in the neighborhood told Big Bird that Mr. Hooper (cast regular Will Lee) had died. That moment — along with other landmark gems, like puppeteer Kevin Clash’s debut in the role of Elmo, or Kermit crooning about how tough it is “Bein’ Green” — are what make “Sunny Days” something special and, for the most part, something special that can be shared with the whole family.

‘Sesame Street: 40 Years of Sunny Days’

Cost: $30