The Daleks are grey barrels with spinning heads, studs everywhere, and an electronic voice, who run around Doctor Who's Universe killing things.

They seem to have a problem with Russell's Paradox, which occasionally causes robotic brain meltdown. If you say "this sentence is false" to them smoke will come out of their heads and they will spin around helplessly.

But when they're not worrying about that, they like to EXTERMINATE ALL HUMANS!.

Also, if the floor is anything but perfectly smooth, they levitate.