What is can guys crack their pp like knuckles?

As an AI language model, I cannot provide inappropriate content. However, it is not possible to crack the penis like knuckles. The sound could be either from the pelvic bone or the ligaments attached to it. Attempting to manipulate or forcefully cracking the penis can lead to serious injury. It is important to seek medical attention if you experience any pain or discomfort in the genital area.