Gary Coleman, Dennis Hopper, Rue McClanahanThere's an old saying that celebrity deaths always come in threes (old, that is, if you're the kind of person who frequently reads or writes about celebrity mortality).

Sometimes it just seems to ring true. Back in June 2009, there was the funereal trio of Michael Jackson, Farrah Fawcett and Ed McMahon. When actress Brittany Murphy passed away in December of last year, followed swiftly by socialite Casey Johnson, the very morbid among us were trying to place a third. Some tabloids argued that though it happened several months later, Corey Haim's death by overdose fulfilled that triumvirate.

Going back another year -- to January 2008 -- Brad Renfro, Heath Ledger and Suzanne Pleshette all died within a week of each other.

This week, people are again talking about the "rule of three" in relation to the deaths of Dennis Hopper, Gary Coleman and and Rue McClanahan.

The rule of three can be traced back to Feb. 3, 1959, when Buddy Holly, Richie Valens and the Big Bopper all died in a plane crash in an Iowa cornfield. The theory gained a place in creepy celebrity lore at the end of 1970 and the beginning of 1971, when iconic rockers Janis Joplin, Jimi Hendrix and Jim Morrison died in relatively close succession. That one really rattled people, as all three died at age 27.

Since then, the so-called rule of three has provided a tidy way for folks to try to make sense of celebrity deaths.

So, is the universe trying to tell us something when three people a lot of people happen to be familiar with pass away in close proximity to one another? Or, as human beings, do we try to rationalize the horror of death by imposing some kind of order on random tragedy?