Joker is the known call sign for at least two pilots on battlestar Galactica (Miniseries, "Act of Contrition").
A restored Viper Mark II had a nameplate for a Lieutenant Pete Mickey, who was likely a Viper pilot assigned to Galactica during the Cylon War (Miniseries).
Another Joker was on the pilot's roster for Galactica during "Act of Contrition".