WHEN YOU ARRIVE at Blue Sky Studios in Greenwich, Conn., he sits there sweetly, fluffily, just waiting for you to approach. Here in the animated home of Seuss’s Horton and “Ice Age’s” Scrat and the occasional “Rio” macaw, there first reclines Snoopy. Hospitality, like happiness, is a warm beagle.

As hundreds of workers dive into the home stretch of production for “The Peanuts Movie,” landing in November from Blue Sky and 20th Century Fox, a giant plush Snoopy might be first to receive you, but there is an evolution of incarnations of Charles M. Schulz’s beloved beagle throughout the offices — from the ground-hugging, shorter-snouted dog of the early ’50s to the tennis-playing, plump-muzzled pet of the ’70s and ’80s, to the new feature film’s 3D version that continues the cartoonist’s line in more ways than one.

As I’m guided to one room, lining the walls inside is Snoopy’s “hero matrix,” which reveals how the Blue Sky artists deconstructed every iteration of Schulz’s black-and-white pooch from every era and built a version that they hope the most number of viewers will be comfortable with, and relate to, as their Snoopy. Most “Peanuts” fans grew up on the Snoopy who would walk upright and stride with confidence, for example, so the artists in this room — Nash Dunnigan, Sang Jun Lee, Vincent D. Nguyen and Jon Townley — show how they broke down the proportions and angles, including those “Picasso eyes” on one side of the face, to give us the movie’s “hero” Snoopy.

And it is here where you’re reminded just how much Schulz visually evolved his characters over time, each as personal as a signature, never getting completely fixed on just one singular, identical look for multiple decades.

That refusal to remain entirely fixed could also explain that although Snoopy was introduced to the world in October of 1950 — the very month the strip launched — Peanuts Worldwide, and thus fans worldwide, celebrates Snoopy’s official birthday today: Aug. 10.

The reason: On this day in 1968, Snoopy walked into a surprise birthday party, so “Peanuts” officials give the beagle his cake-topping candles to blow out every Aug. 10.

Today, the keepers of the “Peanuts” flame are encouraging fans to celebrate by drawing Snoopy and sharing their art on social media using either of two hashtags: #DrawSnoopy or #HappyBirthdaySnoopy. And below, “Peanuts Movie” director Steve Martino draws his version of Snoopy.

Whether your real age is 65, or 47, or some formula that multiplies dog years by anthropomorphic-dog years, let us just say: “Happy birthday, Snoopy!”