Grin is a common parent of the block. Its name derives from the Cheshire cat. The grin has a spark that can be used in the bumper.
In other rules
Grin is a common light-speed spaceship in many B2 rules, the most notable being Seeds and Live Free or Die. It is the third most common spaceship in the former, where it is known as moon. It also functions in cb2.
The pattern also appears as a c/2 orthogonal in some B0 rules, interestingly keeping the same appearance in all phases.
- Moon at David Eppstein's Glider Database