Did you accidentally click the wrong convention to your costume?
Or you thought you were going to wear the costume, but didn't end up wearing it?
You can remove a convention tag from your costume via your control panel.
1. Click
http://www.acparadise.com/acp/tools.php?t=costume&v=1
2. Find the costume you need to correct and click the name of the costume
3. Then scroll down to the bottom and hit the red "x" next to the convention you want to remove