We tend to think of “Sesame Street” as older than we are, no matter our age, because we can’t recall a time when it didn’t exist.

At 35 years young, television’s most influential children’s show may also be its most inconspicuous. You don’t necessarily notice “Sesame Street” until you need it, which is the way parents have looked at it for years. They watched as children, and now they watch their children watch.

But amid the blizzard of toy infomercials disguised as children’s television shows these day, we may need “Sesame Street” — and other shows like it — now more than ever. With its ironclad marriage of education and entertainment, “Sesame Street” remains a proud standard-bearer that is not content to rest on its laurels (or its 75 Emmys).

When “Sesame Street” broadcasts a celebratory prime-time special tonight, the first notion might be to marvel at how little has changed. Big Bird is still tall and sweet, Oscar the Grouch is still short and cranky, Elmo still loud and very red. The pace of the show is still leisurely, the atmosphere warm and welcoming. Preschoolers are still entertained while picking up language skills, numerical concepts, reasoning, problem-solving, tolerance, and learning about the importance of diversity. Major stars, from Yo-Yo Ma to Britney Spears, still pop in to goof off with fuzzy little Muppets. And adults are still as tickled by the show’s charming banter as their children.

But, actually, “Sesame Street” has survived and even thrived because of its willingness to change, and not simply with the addition (or subtraction) of characters. “Sesame Street” has extended its lifeline and raised the bar even higher by acknowledging a subtle but significant shift in how children raised in a media-saturated universe view television.

Let’s remember that “Sesame Street” arrived in November 1969 when the television medium was made up of three major networks and a sprinkling of independent stations. For children, the options were Saturday morning cartoons and a tiny number of shows during early weekday hours, and most of those were geared toward older children.

“Sesame Street” was actually radical for its time, first by lowering its target age to 3 (to better serve preschool children getting ready for kindergarten) and then by airing a program lasting a full hour. (“Captain Kangaroo” and “Romper Room” were half-hour shows.)

“Sesame Street” made its mark quickly, largely because of Jim Henson’s cast of cute and quirky Muppets. They, more than anything else, made the episodes likable and understandable to the show’s viewers.

It’s that same generation of viewers that has since become parents who feel a special bond with “Sesame Street.” Even though the extent of their viewing was two, maybe three seasons, when you ask a baby boomer these days about their favorite “Sesame Street” character (Oscar the Grouch or Grover), the music or moment (the marriage of Maria and Luis), their eyes light up with a glint of nostalgia and emotion.

“I remember being very excited about seeing Big Bird and Ernie and Grover, because as a kid it’s as though they’re just as excited to see you,” says Charlla Feller-Davis, of Fort Worth, whose 2-year-old son, Charles, now watches. “And it took me to different places and introduced me to different people. They lived in this neat city neighborhood. I didn’t get this feel in my really small town in Iowa.”

Tonight’s episode is a nostalgic journey through the show’s many moments, with Elmo learning more about the history of the street on which he lives.

The episode is quite touching, as flashbacks show Mr. Hooper, Maria (Sonia Manzano) and Luis’ (Emilio Delgado) wedding day, the birth of their TV daughter, Gabi (who for a short time was played by Manzano’s real daughter), and the adoption of Miles by Gordon (Roscoe Orman) and Susan (Loretta Long).

The finale features the entire cast singing the new original song “The Street We Live On,” which is fitting for a series determined not to leave any child, or parent, for that matter, out of its loop.