I always assumed that Gamzee hadn't created Cal. I thought he found the Cal that Kanaya had fixed in the memory on page 5498 and sent it over to the kids session through Chuckle Voodoo. Cal is still wearing the Felt outfit when Gamzee does the Chuckle Voodoo.

He didn’t send it over with chuckevoodoo, he created it.  The Cal in the felt outfit is still with him when he’s in the Alpha kids’ session