A is for the Atavachron.
B is for the Breen.
C is for the Chameloids, skilled shapeshifters.
D is for Denobulans.
E is for the Enterprises, all of them.
F is for the Ferengi Rules of Acquisition.
G is for Gagh, something that would make you gag unless you are into Klingon food.
H is for Harry Mudd.
I is for the Inverter, it's like the transporter, but it can't be protected against, on the other hand, the long term effects of its use are serious disease and death.
J is for Jouret IV.
K is for Koloth.
L is for Landru.
M is for Moogie... No comment.
N is for Nibia.
O is for the Obsidian Order, you know them, don't you?
P is for Positronic brains.
Q is for Quadrotriticale.
R is for the Roman-like humanoid civilization that developed on planet 892-IV.
S is for Sim.
T is for T'Pol's bumm....fanclub.
U is for Unimatrix zero, it a resistance movement, actually.