While trying things for the LEGO Racers online mod, I found a way to disable the joystick check.
This means you will be able to play local multiplayer without the need of an extra controller.
To achieve this, a small edit in the game exe is required. I recommend making a backup of your exe file first.
There are two methods to do this:
1. use the automatic patcher I made:
https://ore.rockraidersunited.org/legacy/LEGO_Racers_multiplayerpatch_270543.zip
steps:
1. extract the archive in