Cassiopea on Wiki

Cassiopeia Twin Fang - Twin Fang's cooldown reduction effect will also trigger on the poisons of Teemo, Twitch, and Singed.

Twitch Deadly Venom - Deadly Venom will count as poison for the purposes of the cooldown reset of Cassiopeia's Twin Fang.

I'm confused.

EDIT: And also can't spell Cassiopeia.