Access World 19
Once you officially clear all 18 worlds in the Super Mario Challenge campaign, you will be told that there are expert levels waiting for you if you acquire 40 or more medals. Once you reach 40 medals, W19-1 will be unlocked in Coursebot. World 19 consists of 12 levels, and each new level unlocks when the previous one is completed.
Door Knocking
When making courses, after placing a set of standard Warp Doors (but not P-Warp Doors or Key Doors), you can tap on either door to generate a knocking noise. If you tap the door enough, the door will open for a couple of seconds revealing Weird Mario before closing. This can be done as many times as you wish, and Weird Mario has different poses depending on the Game Style selected. As an example, he may be dressed as Racoon Mario in SMB3, Cape Mario in SMW, or Acorn Mario in NSMBU.
Edamame Profile Icon
If you are able to complete the Super Mario Challenge without using an assist item, you'll be rewarded with a "piece of edamame". It turns out this is a special icon that appears in your profile in Course World. You can find it on the upper right of the profile screen.
Access World 19...