In his capacity as what John Trussell has described as "a big, 350-pound chunk of [the world's] sense of humor," Derek was extremely sensitive to the funny things around him. He also possessed an excellent memory for minutiae (one might even go so far as to call it "trivia"). These two traits combined to create the phenomenon we came to know as "break triggers".

It worked like this: if a joke was told around Derek that was of sufficient power to break him, the punch line of that joke would stick in his memory. Thereafter, if at any point the punch line were repeated to him, he would call up the rest of the joke from memory and break again, unassisted. This was very useful in situations where some people present had not been present for the original telling of the joke, since it would seem to those observers that Derek had been broken by a nonsensical statement such as "Literacy!"

Break triggers I can remember off the top of my head include:

• "Literacy!" This one popped up during a late-night game of Civilization, during that time of the evening when everything is funny. Here's Andrew Petrarca with more details.
  

  Another is the "literacy" story.  This also took place in F13.  We were
  playing Civilazation for the first time, and we hadn't realized haw bloody
  long the game can take...  We had something like 6-8 players, and we didn't
  start until at least 6PM.  Well, we were still playing at 3 or 4 AM, and we
  were making a lot of stupid jokes, most of which were funny only because of
  the hour at which they were told.  Derek was playing Africa, and he'd just
  been struck with a plague (or was it a famine?) that lost him 8 population
  tokens, which nearly wiped him out.  I made a wisecrack in an exaggerated
  "stupid person" voice (sort of like one of Monty Python's "Gumbys") and said
  "Gee Derek you sure lost a bunch of guys on that one-" then I interrupted
  myself, saying in a normal voice "oh, wait a minute, I have _Literacy_."  I
  then adopted an upper-class English accent and said "I say Derek, you seem
  to have lost quite a few tokens on that play."  We all lost it for a good
  long time.
  

• "Paraaaade - of - Shoooes!" This one has its own anecdote entry.
• "Oh yeah? Well, I could just blow my cool roll." Said by Derek as he attempted - unsuccessfully - to knock a hat off the head of someone he was having a good-natured argument with. The failure caused him to give up the argument and then break.
• "WHAT warp coefficient?!" This one is an exception to the usual rule - it has no joke to go with it. It's a meta-trigger. I once wrote a particularly silly Star Trek: The Next Generation fanfic featuring a group of gweeps, including Derek. This was included as one of the break triggers used by the fictional rest of us to break the fictional Derek. For some reason, it amused the real Derek enough to break him on its own merit.
• "Follow the pink, bouncing ball to a doofus!" This one will have its own anecdote entry as well, eventually.
• "Booger!" Dave Barry has officially classified this as an Inherently Funny Word; in addition, it was used once by Crow T. Robot in desperation during a really slow part of a Mystery Science Theatre 3000 episode. Especially effective if said out of the blue, after a long quiet time or conversational lull.
• "Hooray, these pants!" This one also has an anecdote entry all its own.
• The same goes for "(Wide keyhole)."

If you can think of any others I've overlooked or temporarly brain-faded on, please remind me so I can update the list. I know I'm leaving some out here.