It'll always be RROD in my heart.  I still enjoy the memories of when it happened to me and realized that I didn't care that MS made one of the faultiest products of all time.  Then I realized their must be something wrong with my head and that I need to deal with it, but the new 360 came in from repairs and I got distracted.

They also turn red if the optical cable is unplugged. No idea what actually caused the red rings, i.e. why the system overheated so often.

I had that, plugged my 360 in but one of the wires was not in properly, it started flashing red, I panicked, people died.

I think that they knew this could be a problem, but thought that the % of owners with the problem would be much smaller than it ended up.  At some point, they did a calculation of the cost impact versus missing the opportunity to launch in 05'.  They just had bad info from the engineers as to the probable impact %.  Atleast that's my opinion!

hahaha yeah it got me worried the first time too! Its a fun trick to play on your friends.

Yeah that reminds me lol, we had a gettogether with friends and a friend brought his Core 360 he brought when it just came out, me and another mate were in charge of plugging it in while he was playing Ninja gaiden on the 2nd Xbox. We plugged it in, 3 red lights started flashing, we almost shat ourselves haha, the guy whos Xbox it was was like WHAT WTFS WRONG!?