1 Ishmael: {into phone} Hi, I'm calling to volunteer for the space mission to deflect the asteroid, that the government advertised on the net. I have experience dealing with Martian plans.
2 Charity Collector Guy: {into phone} But do you know anything about deploying nuclear explosives?
3 Ishmael: {into phone} Oh please. I'm a science student!
4 Ishmael: {into phone} Give me two bottles of Mountain Dew and 10 hours to cram, and I can fake it!

Mountain Dew is, in the USA at least, a highly caffeinated fizzy drink with a reputation of being one of the potential drinks of choice to invigorate students needing to study all night. Exactly how something labelled "mountain dew", with its connotations of purity and unadulterated fresh water, came to be used for a mind-altering drink compiled mostly of artificial ingredients is a mystery justified only by the minds of teams of advanced marketing technicians with degrees in twisting consumer expectations for massive profit. (Edit: Apparently "mountain dew" is an old American slang term for moonshine, which was adopted by those clever marketing technicians specifically for the connotations of potency and rawness, rather than purity and wholesomeness that come to the minds of people not versed in this lore. Language can be strange sometimes.)

Interestingly, a product named Mountain Dew, also produced by the Pepsi-Cola Company, is also sold in Canada and Australia, but in both those countries it has no caffeine whatsoever, and subsequently no reputation beyond "yet another bland, artificially flavoured, sickeningly sweet soft drink". This rather devalues the mystique of the drink.

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2019-08-31 Rerun commentary: The reason why Mountain Dew in Australia had no caffeine was because of a consumer law that specifies that only soft drinks marketed as "colas" or as "energy drinks" could contain caffeine. So it was actually illegal to sell Mountain Dew with caffeine unless the branding was changed.

In 2012, PepsiCo did exactly that. They launched "Mountain Dew Energised", a new "energy drink" version of Mountain Dew, which was exactly the same recipe as the default Mountain Dew in the United States. Then they withdrew the non-energised version. So now Mountain Dew in Australia is the same caffeine-heavy drink as in the United States, just with a different name.

As someone who never drinks caffeine and almost never drinks fizzy soft drinks, this makes very little difference to me personally.

I don't know what the situation is in Canada.