The following p4 oscillator with a minimum population of four cells, which is a component of many other oscillators, such as the anchor track, anchor stack, buoy, and flotsam. In terms of minimum population, it ties with the lever and radar as the smallest p4 oscillator, but the lever has a smaller bounding box and average population. The only naturally occurring puffer that generates anchors is the ferry puffer, but anchors can be produced by flotillas in various ways.

anchor.png

x = 2, y = 5, rule = s0/b2
bo$o2$o$bo!