Season S is a season of episodes of the YouTube comedy series The Lenny Leggo Show. It is a special season that is separate from the rest of the main series. The "S" in Season S stand for "special".
There are several differences between Season S and the numbered seasons: the biggest difference is that the latter makes up the primary time-line/canon of The Lenny Leggo Show while the former is entirely non-canon to The Lenny Leggo Show. Instead, this season includes episodes of certain, alternate timelines and events that would otherwise contradict anything in the main series: for example, the first set episode for Season S is essentially the show's YouTube channel trailer, which is actually set in the real world, known officially as the Studio Continuity, rather than the fictitious world that the rest of the show takes place in. It is also possible for Season S episodes to be non-canon to each-other, although all episodes in the studio continuity are assumed to be canon to each-other. Furthermore, an animated Season S episode may be a sequel to another animated episode, or an episode's are referred to in a later one.
Another main difference is that, unlike the numbered season episodes, Season S episodes do not have a standardized running-time. While numbered season episodes run for approximately 25-30 minutes, Season S episodes could be just about any running time.