Wii U Friends List custom keyboard hack showcase
32Gecko dotNET and an old version of the TCPGecko Codehandler was used to pull this off, which involved downgrading the browser files to run exploits made for firmware 5.5.1.
Using Gecko dotNET, I was able to push data to the SWKBD addresses which made the hacked symbols show up. These addresses were really easy to find.
In the example shown here, I pushed 3 different BIN files to the keyboard, and loaded them by switching to Caps Lock and back, or by reloading the keyboard.
This works with both your Wii U Friend List message and messages you send in Friend Requests.
The SWKBD files were not modified directly, meaning the keyboard goes back to normal when you exit the friend list.
If you want to try this yourself, and you know how to use Gecko dotNET, you can download the BIN files used here: https://cdn.discordapp.com/attachments/882425590093873193/908525768190095410/SWKBD_Friends_List_Modded_BINS.zip
The location for SWKBD in Hex for the Friends List is 235FE3F8 (EUR version, haven't tried on USA or JPN yet due to lack of access)