A is for Also, Picard's faux family celebrated Christmas in the Nexus! 
B is for B'Elanna's Klingon heritage.
C is for Circus Clowns hired for Picard's sixth birthday's party.
D is for those nifty t-shirts with "DISCO" emblazoned on them.
E is for the Excelsior, Sulu's ship.
F is for Funny Trek Episodes involving Ferengi like Little Green Men.
G is for the Gorns, they're referred to far more often than we see them.
H is for Holograms. They caused an uprising in the novelverse, protesting against their slave existence.
I is for Ingraham B.
J is for Just a fact check, but Gorn have made three appearances (Arena, Time Trap, IAMD), not counting the skeleton (Discovery episodes), but only referenced in three other media (Trials and Tribble-ations, Bound, Into Darkness). They're appearance/mention ratio is even or high depending on the skeleton.
K is not for O.K. if you say so, but that could also be counted as six mentions (since they're obviously mentioned in the episodes where they appear) and three appearances. Six was (far) more than three, the last time I checked.
L is for Lurians, who appear more often than they were mentioned.
M is for Murder, something that applies to kill your own clone or not, depending on the series you're in.

B is for B'Elanna's Klingon heritage.
C is for Circus Clowns hired for Picard's sixth birthday's party.
D is for those nifty t-shirts with "DISCO" emblazoned on them.
E is for the Excelsior, Sulu's ship.
F is for Funny Trek Episodes involving Ferengi like Little Green Men.
G is for the Gorns, they're referred to far more often than we see them.
H is for Holograms. They caused an uprising in the novelverse, protesting against their slave existence.
I is for Ingraham B.
J is for Just a fact check, but Gorn have made three appearances (Arena, Time Trap, IAMD), not counting the skeleton (Discovery episodes), but only referenced in three other media (Trials and Tribble-ations, Bound, Into Darkness). They're appearance/mention ratio is even or high depending on the skeleton.
K is not for O.K. if you say so, but that could also be counted as six mentions (since they're obviously mentioned in the episodes where they appear) and three appearances. Six was (far) more than three, the last time I checked.
L is for Lurians, who appear more often than they were mentioned.
M is for Murder, something that applies to kill your own clone or not, depending on the series you're in.