My buddies and I are a bit confused when it comes to stunned characters and some different effects. I'll give you a few examples:

1. If you have only one stunned character in the support row, is that character present in the support row? This came up when one of us plays Surprise Assault. We don't know how much damage you should take.

2. Can you put +1/+1 counters on stunned characters?

3. Can stunned characters be targeted by cards that just target a character?

Anything else you can think of to add to go along with this would be a great help. Thanks in advance.

1. The player with the stunned support row character(s) would take 3 endurance loss from Surprise Attack. Stunned characters basically just lose their text and their protected status.

2. Yes you can, there's no restriction on this.

3. Yes they can. Cards such as Flying Kick that say, for example:

has no restriction that the character must be un-stunned so you can definitely target a stunned character.

As for additional information, here is the entry on stunned characters from the comprehensive rules document:

By the way, since there's not many people around this website anymore to answer questions, you might want to check out www.VSSystem.org. You'll definitely get quicker answers there than here.