The "Mickey Mouse" comic strip drawn by Floyd Gottfredson was generally based on what was going on in the Mickey Mouse shorts at the time, but when Donald Duck's popularity led to Donald Duck gaining his own newspaper strip, Disney decided that he was no longer allowed to appear in Gottfredson's strips. Accordingly, Goofy remained alone as Mickey's sidekick, replacing Horace Horsecollar as Mickey's fellow adventurer and companion. Similarly in comics, the Mickey Mouse world with Goofy as Mickey's sidekick was usually very separate from the Donald Duck world and crossovers were rare.