Walt Disney's last script for the strip appeared May 17, 1930. Gottfredson's first task was to finish the storyline Disney had started on April 1, 1930. The storyline was completed on September 20, 1930, and later reprinted in comic book form as "Mickey Mouse in Death Valley". This early adventure expanded the cast of the strip which to this point only included Mickey and Minnie. Among the characters who had their first comic strip appearances in this story were Clarabelle Cow, Horace Horsecollar, and Black Pete as well as the debuts of corrupted lawyer Sylvester Shyster and Minnie's uncle Mortimer Mouse. The Death Valley narrative was followed by "Mr. Slicker and the Egg Robbers", first printed between September 22 and December 26, 1930, which introduced Marcus Mouse and his wife as Minnie's parents.