[Bells]

Not really, the other three have been more well known. He probably just wanted to make a comeback and wasn't bothered which he went on. And to be fair, think about the way he was treated when he first entered - it was difficult afterwards yes, but to begin with he was like a King put in a house full of girls. He seemed to get special treatment, which he probably got due to his past status... i.e. he's quite good-looking etc. and that's exactly what the girls in the house were after. He certainly wouldn't be getting the same if he went on CBB.

EDIT: Not to mention if there will even be one after the past CBB5's chaos... normal BB is better anyway IMO, and if BB producers are to select housemates for CBB they ought to be a lot more careful. So as Ziggy was interested, another possibility is that they just put him into the normal one anyway.