The missing pair from the list is "Cherry and Key Lime."
To see this, we recognize that there are a total of 6 unique pairs that can be created from the 4 types of pies (Cherry, Apple, Blueberry, and Key Lime). The pairs are:
- Cherry and Apple
- Cherry and Blueberry
- Cherry and Key Lime
- Apple and Blueberry
- Apple and Key Lime
- Blueberry and Key Lime
From the list provided, we can see that the only pair not mentioned is "Cherry and Key Lime." Therefore, the answer is:
Cherry and Key Lime