The Half-Life games are amongst the most mysterious in contemporary video games. The development of each title is shrouded in secrecy which, alongside the endless delays that plague the release of them, only serves to make them all the more beguiling. Developers Valve tend to play their cards pretty close to their collective chest, teasing out only the smallest morsels of information prior to the (eventual) release. Right now fans are clamouring to know everything about the third in the series - and if there even is a third in the series - but there's enough in the existing titles to be digging into. The original Half-Life hit PCs in 1998; the sequel finally dropped in 2004. That means, between them, the Half-Life franchise has at this point been around for fifteen years. In that time, only a handful of the secrets, Easter eggs, and weird ephemera to do with the series has been uncovered. There's still plenty of amazing facts, bizarre trivia and unused content to pour over as fans wait with bated breath for any sort of confirmation about another Half-Life from the Great Lord Newell. From celebrity fans to enemies that didn't make the cut, from happy accidents to weird Japanese stuff (really, the "weird" in that phrase seems a little superfluous) these are ten things you didn't know about Half-Life.