A is for Adam. Yea, brother, we reach!
B is for Bibi Besch, who played a middle-aged Carol Prime.
C is for Captain Leo Walsh, better known as Harry Mudd.
D is for Deneb IV, first visited by Starfleet officers at some unspecified date prior to 2265.
E is for Engrams from Richard Daystrom impressed onto the M-5 Multitronic Unit.