The details of the noodle incident were never fully revealed. We can assume it was an event involving noodles that was probably influenced by Calvin's overactive imagination and for which he got into serious trouble. Calvin and Hobbes referred to the noodle incident two or three times throughout the run of the comic, but Watterson never drew it out. Whether he had anything specific in mind... you'd probably have to ask Watterson.

I remember reading somewhere that it had something to do with science class and a container of pasta that Calvin had brought to school sometime in an earlier strip...still trying to find that strip. I'd guess he was trying to exchange the brain for pasta and got found out or maybe he blew one out his nose during lunch time and was getting teased.

A running gag that was introduced slightly later on during the comic. Whenever a character, usually Hobbes, mentions it to Calvin, he immediately gets very defensive about it. We never see the Noodle Incident itself, nor do any of the characters ever explain what events transpired. Watterson mentioned he kept it this way to leave it to the reader's imagination. These are the only facts we know about the Noodle Incident: It took place at school. When Calvin's mother returned home from meeting Calvin's teacher, he immediately asked if she had been told about the noodles. It was a while ago, and therefore, must have been a very serious incident for it to still be remembered. To try and prove innocence, Calvin apparently thought of a cover story, the creativity of which impressed Hobbes. Calvin, however, even now claims that it was the "unvarnished truth". Like the incident itself, we are never told exactly what Calvin's excuse was. It is not exactly stated one way or the other, but it seems to be implied that Calvin was caught, therefore his cover story was not believed. According to Calvin, although apparently caught, no one can prove he did it. However, considering Calvin may just be defensive about it makes such a statement questionable. The fact that Hobbes repeatedly brings it up (as did Santa in Calvin's imagination once), seems to imply the memory still haunts Calvin to this day. Although it is not certain, it is believed that the Noodle Incident had to do with when Calvin was sent home early. "Did it have something to do with those sirens around noon?" The strip in which that quote is directly preceded by one in which Calvin states he will "go for the gusto" at school.

The TLDR version of Ed's answer: The noodle incident is, as Ed said, a running gag on the comic strip Calvin and Hobbes. It's never explained in the comics, similar to Hamster Huey and the Gooey Kablooie, and it is left to the reader's imagination.

I'll be looking forward to "doodlethenoodle" comment on this.

The Noodle Incident was never an actual comic strip, we can only guess what it might be. It's like a myth throughout the Calvin comics, often used as reference to bring out Calvin's guilt or his defence to underline an existing strip concept.

The Incident where they sometimes bring it in the strip and Cavin or Hobbes get defensive about it.

It may have had something to do with the time when he had to do a presentation on the brain and was going to use a bag of noodles for his visual aid. It is interesting to note that he did not have the noodles during the speech.

1) "In the later years of the strip, with more space available for his use, Watterson experimented more freely with different panel layouts, art styles, stories without dialogue, and greater use of whitespace. He also made a point of not showing certain things explicitly: the "Noodle Incident" and the children's book Hamster Huey and the Gooey Kablooie were left to the reader's imagination, where Watterson was sure they would be "more outrageous" than he could portray." "Both the Noodle Incident and the book Hamster Huey and the Gooey Kablooie are mentioned several times in passing, but Watterson left the details to the reader's imagination "where [they're] sure to be more outrageous". Noodles are first mentioned in connection with a report on the brain, and later Calvin worries that Miss Wormwood told his mom about "the noodles", but it is never stated whether these are related to each other or to the Incident. The strip even depicts Santa's research department having trouble discovering the particulars of the Noodle Incident, and every mention of the incident brings forth vehement denials of involvement from Calvin." Source and further information: http://en.wikipedia.org/wiki/Calvin_and_Hobbes 2) here some theories: "Calvin decides to try to cook some noodles at the school cafeteria VERY early in the morning (Hobbes has been brought along) and starts making LOTS of noodles. So many, in fact, that they start to overflow the pots, then the room, the school. But by that time school has started and the kids and falculty are there, and the public safety departments must evacuate everyone from the school. Calvin tries to claim it was an accident." "I think Calvin and Hobbes planned to do something to really gross out Susie (like usual). So they went to school, cooked noodles like you said too, and poured pots worth of it into her desk, so when she'd open it up, she'd get a big surprise, and Calvin would say something like, "Hmm, nice baby octopus legs," or whatever" Source and further information: http://forums.toonzone.net/archive/index.php/t-5911.html Further information: http://thenoodleincident.org/ http://www.answerbag.com/q_view/158292