On Lycanthropy

Each form of lycanthropy is limited to one base race.  For example:

Werewolves come from humans;
Wererats come from halflings;
Wereboars come from dwarves;
Weretigers come from elves/half-elves;
Werebears come from orcs/half-orcs; and
Werecrocodiles come from lizardfolk.

As a curse, lycanthropy generally is meant to conflict with the nature of the base race.  Thus, werewolves, wererats and wereboars are evil (whereas humans, halflings and dwarves are generally good), but werebears are good (whereas orcs are generally evil).  Weretigers are neutral (whereas elves are generally good).  Werecrocodiles are evil (whereas lizardfolk are generally neutral).

In all three forms, wererats are size small.

Werebears, weretigers, and werecrocodiles are size medium in hybrid form.