This just in from Jim Korkis:

[This week you featured a fascinating picture of Walt going to court over Mickey's Polo Team. Actor John P. Wade claimed that he had submitted a script to Walt and Walt claimed it was unusable but when Wade saw the finished cartoon, he felt that Walt had taken his ideas. I had never heard this story before and assumed it was just another of the many nuisance suits that are filed against the Disney Studio by authors who feel their stories are similar to Disney animated cartoon stories.

Anyway, to clear up the matter here is an excerpt from TIME magazine (January 24, 1938) that clears things up a bit:

When Actor-Author John P. Wade saw the Walt Disney cartoon, Mickey's Polo Team, he sued Disney for a share of the film's profits. Alleged plagiarism: that the gag of the horses riding the riders had been lifted from Author Wade's skit, The Trainer's Nightmare. In court, attorneys for Cartoonist Walt Disney identified the device as a variation on "the reversal gag," easily traced it to Aesop. Said Superior Court Judge Thomas C. Gould, dismissing the suit and plagiarizing Ecclesiastes: ". . . It appears there is nothing new under the sun."]