It was with John W. Campbell, who was egged on by Robert Heinlein. Both Heinlein and Hubbard wrote for Campbell. The three of them were at a table at a WorldCon together, and were not particularly sober; Heinlein, being a sailor, held his liquor better than the other two and decided to have some fun. Hubbard was drunk enough to agree.That Hubbard was one of Campbell's writers, by the way, is another sign that Hubbard wasn't a 'failed' writer. Failed writers got rejected from Astounding/Analog.