people who suddenly become sexually active or horny only by night, never during daylight hours. usually appear quiet and shy by day but change by nightfall.
oi son, that old gaffa iza right genuine nightweasel!
for someone to do or say something completely randomly (out of the blue) for no-ones benefit, not event their own, (almost a change in personality). a scrat can appear controversial, and can either offend or humor, but possesses no worth.
a scrat can occur when driving calmly, then a sudden change takes place to an eratic mood.