List of speculated meanings behind the comic

Below is a list of speculated meanings related to the periods of Time or Time itself.

Randall died

By now I think we can be certain he hasn't died

To make the most posted forum topic something other than a massive flame war

The most posted forum topics are mainly flame wars. 

Its just a freaking sandcastle... don't read into it...

It's way more than a sandcastle. Cueball and Megan have been away from the sandcastle for so long now, I've almost forgotten about it.

April Fools Lead-up

The comic is published exactly one week before April Fool's day. 

Since April Fools is long past and the comic is still updating, it is unlikely that the purpose of the comic is an elaborate April Fool's joke.

On the other hand, there is always another April Fool's day next year... or the year after that.

Taking a vacation and wanted something to keep our attention

Randall is on vacation when the comic is published.

Game of Thrones

Homage to opening sequence and countdown to start of season 3

The whole sandcastle-building is just foreplay

As seen in frames 161 and 175, Cueball may have just got out his "population control".

Randall is trying to take over the world, not including the Outside, using HoIP

HoIP stands for Hypnosis over Internet Protocol.

MMONS

Main article: MMONS

MMONS stands for Massively Multiplayer Online Nerd Sniping.

It references http://xkcd.com/356/

First used here: http://forums.xkcd.com/viewtopic.php?f=7&t=101043&start=640#p3303276

A meditation on the perception of time/story

• The presentation is opaque with regards to the actions of the author. Does he have a master plan? Is there a definite ending? With what frequency does he update frames (were they all drawn in advance, or does he draw new frames every so often?).
• The whole story is not available to the readers immediately - they are forced to wait for updates which come at a seemingly glacial pace. Does this have relevance to the speed at which people think? Does the reader hold assumptions about how content should be presented? Previous comics have seemed like progressive exercises in Nerd Sniping, but perhaps they were more of an effort to force the user into exploring the topic presented in a specific way. If, for example, "Click and Drag" could not simply be dumped and reformatted to be zoomable, the user would actually have to explore it in a more organic manner. Perhaps this is what Randall is aiming to do.
• With regards to the author, if no outside action is taken, the story will be unavailable to the reader once it has passed. The story is presented in a way that requires others to record it - if others store the history of the comic, then it can be recalled.

An Allegory about Science

The two characters can be seen as stand-ins for humanity trying to understand its universe. At first they just build stuff until they notice notice a threat that sparks their curiosity, and they've been driven by curiosity ever since. And I definitely think Randall is on their side. Granted, as an allegory it's a bad match since the real scientific revolution wasn't driven by any kind of environmental threat. But exact matches really aren't essential. Or they can just be seen as two people trying to understand their world, but it's interesting that it seems as if they have had no outside social contact. Nobody has told them about the mountains or the other rivers. In any case, it's obvious that inquisitiveness is a motivating theme.

This isn't meant to contradict the above analysis that it's "a meditation on the perception of time/story". Whatever else it is, it's clearly that.