Here's why:
* Prune knuckle: This is likely a mispronunciation or a play on words. It sounds similar to "prune" which is a dried plum. However, there's no real connection to knuckles or anatomy.
* Shar-Pei: This is a breed of dog known for its wrinkled, loose skin.
The Commonality:
The only real connection is that both words sound similar to something else ("prune" sounds like "prune knuckle" and "shar-pei" sounds like "shar-pay"). This is a common technique in jokes to create a humorous misunderstanding.
Let me know if you'd like to try another word puzzle!