I pop my knuckles, all 3 thumb joints, wrists (by pronation of hand and supination of forearms, or vice versa), elbows (by hyperextension), shoulders, and cervical vertebrae on a regular basis, and occasionally thoracic vertebrae, toes, and hips. I can very rarely manage to pop one knee or the other, or lumbar vertebrae. I have never been able to pop anything in my ankle; there's just too much joint stabilization there. But I can manage the metatarsal-cuboid joints sometimes by twisting the foot from the toes.

If you can snap your ankle every time you move it in a particular way, it is probably not the same thing. I have never been able to pop the same joint twice in rapid succession. Indeed, that's why I pop so many different joints. Once you've done them all, there's no choice but to wait.

I'd certainly be wary of pops emanating from joints without a great deal of natural range of motion, or those so wrapped up in muscles and ligaments it is practically impossible to isolate any one joint in particular. If you experience any pain while joint-popping, stop doing it, immediately.