He randomly becomes unselectable sometimes in the select screen, requiring a restart of the game.
I have had that happen. It starts with just one character, then speads. The next game it is a few more gray boxes, then even more the next game. I had the same problem with the stages.
Sometimes I see the gray boxes pop up, but for me the characters and stages are still selectable and their names still pop up when you scroll over them. I still restart every time it happens since one aspect of a game glitching usually precedes a load of other issues.