A is for Art. Commander Data enjoyed painting during his time aboard the Enterprises-D and -E.
B is for Beagle. Captain Archer enjoyed playing with his Beagle, Porthos, in his spare time. Just don't feed him any cheese.
C is for Cardassians. They spent much of the 24th century in direct or indirect conflict with the Federation and other powers.
D is for Dominion, the rulers of the Gamma Quadrant.
E is for Eggs. Will Riker kinda sucked at cooking them into an omelette.
F is for Fencing. Guinan and Picard shared a few matches on the holodeck.
G is for Gowron. Chancellor of the Klingon High Council for almost a decade.
H is for Heisenberg compensators. Vital component of the transporter system.
I is for Io. A moon of Jupiter. One of the first NX warp tests in the 2140s catastrophically failed near Io.
J is for Janus VI. Homeworld of the Horta.
K is for Klaang. He was the Klingon who crash landed near Broken Bow, Oklahoma and made official first contact with Earth humans.
L is for Lycosa Tarantula. Obrien kept one as a pet.
M is for Minshara, or M-, class planets.
N is for Neural Parasites. They don't even look real!
O is for Omega particle, the closest thing to a god the Borg have.