I was friends with a couple of junior officers in the crypto community, one of whom got his commission via the LDO (limited duty officer) program. He told me that non-academy graduates called them Ring-knockers. If there was a dispute between 2 officers of equal rank but one of them was a USNA grad he would knock his ring on the table, thus ending the argument.
As for Mustangs, I know 2 guys I went to boot camp with who just last year retired as Captains (O-6 for the non-Navy types). They both got their commissions through the Seaman to Admiral program. As far as I know there has only ever been one SEAL Mustang to make O-7.