Imitation is the sincerest form of cover design, apparently

A good-time browse can be had at theblog Doppelgänger Design where illustrator Brian Taylor posts uncannily (and sometimes suspiciously) similar cover designs and where you can see how a good idea (as above, Cheap Eats) can proliferate.

There are even examples of where magazines imitate themselves, as in this Rolling Stone clone of a "Friends" cover by a "Glee" cover.