This mod allows you to switch characters by holding buttons on the controller while loading a level or during a level by holding the Z button (RB on Xbox controllers with Input Mod). Up to four players may play simultaneously. Controls: Left - Sonic R - Tails Down - Knuckles Right - Amy L - Gamma Up - Big X - Eggman Y - Tikal B - Metal Sonic Start - Drop Out (P2-4 during game)
Additionally, players may press the C button (LB) and a direction on the D-pad to teleport to another player, and player 1 can press the D button (Back) to control player 2's character.
The mod also has some options in the mod.ini file to select the default character to replace Tails in Sonic's levels and the opponent in Tails' levels, as well as toggling the character indicator arrows.
Would it be possible to update the Character Select mod so that you can tell the game to spawn up to 3 AI partners of your choice with any character, instead of only one AI partner with Sonic? It'd be cool to do that for this mod, so that you can have Knuckles and Tails follow you at the same time.