One of the most memorable things about xkcd’s (in)famous circuit diagram is the 666 timer (at the top right corner of the comic), a parody of the famous 555 timer:

Today I was analyzing the logic board for HP 3560A and noticed some batches uses a MAX666 chip and it immediately reminded me of this xkcd joke. Turns out Maxim Integrated makes a voltage regulator with a cool part number! I bet the engineers back in the days must have started with 666, giggling uncontrollably, and added 665 and 664 to see if it can get past the regulators or the censors (puns intended for both).