Alternate timeline
(covers information from an alternate timeline)
Cary McCrystal was a Starfleet officer.
In an unknown, alternate future timeframe, he was named as a Fleet Ops officer on the dedication plaque of the USS Pasteur. (TNG: "All Good Things..." dedication plaque)
This character was only mentioned in writing.
He was named for Second Assistant Camera Operator, Cary McCrystal.