In production order (which the Region 1 DVD release is based on), "The Astrosmurf" is the fifth episode of Season 1. As such, it is the debut of Dreamy, one of many Smurfs created by Studio Peyo for the cartoon series.
In the original comic book version ("Le Cosmoschtroumpf") the Sclips (original French name of the Swoofs) had red skin, not green skin as depicted in the cartoon version. The change of skin color in the cartoon color was to eliminate any racist connotation. Also, Gargamel, Azrael, and Smurfette are absent in the comic book version.
Adapted from the original comic story "Le Cosmoschtroumpf" which was serialized in Spiriou in 1969 and published in its entirety as an album in 1970. While the Smurf who became known as Astrosmurf is Dreamy in the cartoon version, in the original comic, he is unnamed.
In the original comic, Papa Swoof had black hair and beard, unlike the white hair and beard he has in this cartoon version.
In the original comic, the Astrosmurf had to undergo two more Swoof challenges (fight against a "strong" Swoof, and climb a mountain to get an edelweiss before nightfall) that were removed in the cartoon version.