To actually be able to play with these mods, you will need either Dolphin, CTGP, or the MKDS Standard Kart Riivolution Distribution. You'll also need CTools, for editing some files. In order to open them, you'll need a tool called BrawlBox, a tool that is designed specifically for these types of files. But, there are these 'szs' and 'brres' files that you don't know how to open. Let's say you were to get this Shadow Mario Mod, and wanted to use it. Section 2: Understanding how to use/view them
If you don't want any of the mods here, you can try looking on the Custom Mario Kart Wiiki. That website has been running for about 10 years and is not a virus. To find a custom character, you can try browsing this game page. I have never done a tutorial before, so forgive me if this doesn't help much. This tutorial is only for completely replacing characters with custom ones, not making custom characters. HEY YALL IT SEEMS THAT THE FRICKIN UH STUPID THINGY WIISCRUBER TOOL MURDERS YOUR MKWII ISO LMAO SO IF YA WANNA GET THIS STUPID MODS ON YOUR DOLPHIN EMULATOR REFER TO THIS TUTORIAL LOL
