For Megaman X Series:
Level 1: Rotator Cuff Naked Mole Rat
Level 2: Artsy Dragon
Level 3: Couch Cushion Hippo
Level 4: Clammy Lion
Level 5: Spiral Stool
Level 6: Giggle Eagle
Level 7: Pedestal Spider
Level 8: Duff McWhalen (Doesn't need changing)
Levels 9-12: Sigma's quirky brothers, delta, pi, and finally mu.