period 2 oscillator that was found by Simon Norton in May 1970. It is the second most common naturally-occurring oscillator, although blinkers occur more than a hundred times as frequently. It is also one of very few known oscillators that is a polyomino in one of its phases. Toads often appear in large, complex patterns because of their ability to eat things when paired together (as in killer toads). Additionally, toads are useful as building blocks for constructing large oscillators with periods that are a multiple of two because of the various ways in which they can be hassled.