As noted last time, Mickey's role in his own cartoons was going to be changing, and soon. The earlier Mickey cartoons had him being a bit raucous and rough, but his popularity made it imperative that he be softened up a bit. Losing some of the early spirit of Mickey's character demanded that other characters be brought in to pep things up!
Here's "The Delivery Boy," which not only features Minnie Mouse, but also Pluto.
Yes, Mickey's a bit rowdy here, but nowhere near as much as his earlier cartoons, where he'd turn farm animals into musical instruments! Here's another Mickey cartoon from the same period, "Barnyard Broadcast":
In this one, Mickey's really acting as straight man for the supporting cast of Minnie, Pluto, Horace Horsecollar, Clarabelle Cow, as well as the cat and kittens.
Disney was also responsible for bringing Technicolor to cartoons, and in 1932, he released the first Technicolor cartoon, "Flowers and Trees."
Disney, after the success of this cartoon, decided to use his "Silly Symphonies" as a kind of proving ground for fresh ideas and new talent, and would soon hit the jackpot again with what is probably the most popular and well-known of that series!