Radroach's

Whenever a artifact enters the battlefield
under your control, create a 2/2 black
Mutant Insect creature token.
If you control four or more artifacts,
create a token that's a copy of Radroach's instead.
The insect colloquially known as the Radroach is one
of the most ubiquitous denizens of the modern American landscape
-Encalve Field Reaserach Terminal