Here is another TUFF Puppy and Bleach crossover pic!

Snaptrap is the main villain of TUFF Puppy, but he honestly wouldn't fit the role of Aizen. Instead, Grimmjow was chosen because he's very arrogant and one of Ichigo's main rivals.

Ulquiorra is The Chameleon because both are smart and, quite frankly, appear to be rather sad (sometimes for Chameleon) looking characters. lol

Also, Snaptrap and Chameleon don't always get along, which is very true for their anime counterparts.