A rotational multi-author comic series, commonly referred to as an MAS, is a comic series in which the authors agree upon a certain rotation and make their respective comics in a set order. This is not to be confused with non-rotational multi-author series.
The series to make use of this structure was Project Klinkerpoop. When the series was restarted by ToaSidorak after the original Freewebs became inactive, the authors agreed to make their comics in a set order, marking the first true MAS. As a result, rotational multi-author series were originally termed "Klinkerpoop series."
Operation: LOSER was the second comic series to use the MAS format, originally consisting of "group flunkies" who had not been accepted into Klinkerpoop. As time progressed, numerous other series adopted the format. It has since become a fixture in the BZPower comics forum.
As originally envisioned by Project Klinkerpoop, the purpose of the MAS is to create a wacky and unique storyline by allowing each succeeding author to build off the plot of the prior comic. However, as the genre has evolved, this has not always been the primary concern.
The MAS format in plot-based comics
In plot-based comics such as Generic Quest, the plot is taken much more seriously that it would be in a more humorous series. Subsequently, authors often feel the need to more carefully control the direction of the plot. As of late, plot-bases MAS's are noted for long delays between comic releases, as each author is compelled to include a great deal of storyline material. Authors tend to coordinate the plot direction with themselves in private conversation, a out-of-order comics are fairly common due to certain needs relating to the storyline.
Because of the difficulty involved in coordinating multiple authors to post comics in a timely fashion, long wait times between comics in an MAS are common. To solve this problem, many MAS use a bi-rotational system that prompts two authors at a time to make a comic. The most notable series of this kind is Heroes.