This only works for a certain date range. For example, right now you can see the dates from July through Thanksgiving but not the rest of the special days. As the year changes, so does the range if you change your clock manually.If you have a PC, double-click the time in the bottom-right corner. Choose the day as September 11, then press Apply. Then go to muppetcentral.com and that banner will show up! Just make sure to change your computer calendar back to the proper day once you're done. This works for all of the days that we have special banners, in my experience.