Adding extra characters (move if I'm in the wrong topic)

Good day to you all. I'mma get to the point. In SRB2, one of the characters you can play as are Sonic and Tails (with you as Sonic, and Tails following you). I thought that besides SRB2JTE, i thought there wasn't a way for another character to follow you. Until I got the HMS123 wad, one of the HMS character has another clone following you. I was wondering how can I add another character to follow me? For example, if I played as Shadow and I wanted Metal Sonic to follow me, I think I need a WAD editor but I'm not sure how I can add another character.

Yes, you need a WAD editor. I might suggest SLADE, it's probably the best out of all of those existing.

In your OBJETCCFG lump, you can change the SkinName to "SKIN&SKIN" instead of just "SKIN"
For instance, putting "SKIN&SONIC" (Skin being the character you pay as's skinname), a Sonic bot will be added when you play it in singleplayer.

So here, it would be "SHADOW&METAL_SONIC" , I believe.

thank you. after i done that, how would i be to add the option to play as Shadow and Metal Sonic (like they have for Sonic and Tails)?

Well, whenever you will select Shadow, a Metal Sonic bot should spawn.
...Oh also, sounds pretty obvious, but make sure Metal Sonic is also added in the game, else it's likely to output you a Green Sonic.

no i mean like, there's an option for just Sonic and there's an option for Sonic and Tails. I was wondering how do i add that option, so the characters would show "Shadow" and another character would show "Shadow and Metal Sonic", and how do i add a picture for that extra slot to play as Shadow and Metal Sonic?

EDIT: How do i make a picture for the character select screen.

EDIT2: alright i know how to make pictures and edit stuff from their wad files.

tbh (to be honest, this should be locked and left here so other fellow members can save time when they want to know how to do the same.)