Ben Zimmer wrote this one up on Language Log a year ago. Here is my summary of that article.
It originated in Luke 12:24 of the Bible, X0 being both “consider the crows” and “consider the lilies”. “Consider” is translated from the Greek “observe fully”, so when using this snowclone, you’re instructing the reader to think carefully about X and compare some of its qualities to himself. X must be restricted to flora and fauna in order to evoke the original, and famous instances include daisies, cod, fish, termite, oyster, armadillo.