In Super Monkey Ball 3D what are the new characters suppose to be?

Im kinda confused on who or what they are. I am not asking about Jet or the other characters from former games. I'm asking about the characters called C AiAi and W MeeMee and the others that have the same names as other characters but have a letter in front of them. Are they really new characters or just different colors of the other characters or do they wear costumes and the letter is short for something? Any images or video of them would gladly be liked (as I can't find any). Also do you if every character is playable in every mode. I know Jam wasn't playable in Step and Roll and I'm curious to see if some of the other characters are only available in the party modes.