Talk to any shopkeeper on the streets, and they will give you a simpler task similar to the animation frame tasks. You do not need to complete Dr. Fret's task.
If you do accept Dr. Fret's task from Toon Headquarters, visit him at Dr. Fret's Dentistry on Alto Avenue in Minnie's Melodyland. He will request that you defeat 10 Number Crunchers in Minnie's Melodyland. Upon returning, he will then ask you to defeat 20 Cashbots in Minnie's Melodyland. Once you return to him again, he will finally ask you to take down a Cashbot cog building. When you do so and return to him, he will grant you teleport access to Minnie's Melodyland.
The ability to teleport to Minnie's Melodyland