I must have missed this a couple weeks ago, but TNI had news of a Mattel update regarding the Chemo Collect ‘N Connect figure:

A lot of fans have asked about the two types of Chemos showing up at retails. Simply put, we made a running change half way thought production to add a bubble piece inside of his chest to create a cool liquid effect. (we actually tried real liquid but that was not working out!)

I pity the collector who tries to get all variants of a figure in scenarios like these.