Nosey is one of several Smurfs created by Studio Peyo exclusively for the cartoon series. "The Lost City of Yore" is his only appearance.
This is the only Smurfs episode to be animated at Filman, an animation studio in Madrid, Spain (headed by Carlos Alfonso and Juan Pina) who did a lot of animation work for Hanna-Barbera between the early 1970s through the mid-1980s. This explains why the backgrounds look different from Hanna-Barbera's in-house and Australian units.