That's because Smash for WiiU has a low quality model for most characters, and they are used in 8 player smash instead of the normal model, to ensure less polygon counts and whatevs so the game keeps its 60fps intact, if you remove those LQ models the game uses the normal models and it either lags like hell or simply crashes.Funny, Super Smash Bros runs 60 fps with 8 people on screen and full HD *shrug*
What didn't you understand xDIf only there were TCP Gecko cheats that remove the frame limit