I've never understood how cat's can handle variety. I see people buying variety packs of can food and wonder how their kitty handles it.

Thumper when we brought her home from PetSmart, they had her on kitten food for week she was there. Thankfully she did ok without benefit of mixing food when we brought her home. When we've had to switch everyone for weight reasons etc we have to take it slow. It's been my experience when switching foods to mix old with new until they get used to the new. Learned the hard way we didn't mix long enough.