Friends may have bowed out over a decade ago, but thanks to endless reruns it still remains a rock of modern pop culture.

People are still obsessed with the show, working out how much coffee the characters drunk, or coming up with strange theories about the ending. Now a new mystery has emerged – but it’s from one of the show’s DVD covers. Twitter user Ted Fox tweeted a snap of the fourth season DVD, and asked an important question: Why is Rachael the only one with her eyes open? https://twitter.com/thetedfox/status/883342869674766336 Does she know something the others don't? Is she plotting to kill them while they sleep? Why does it look like she's staring directly at us? Other people started chipping in with theories: https://twitter.com/terrybain/status/883344839026200576 https://twitter.com/Burghpunk/status/883343266049118208 https://twitter.com/Bobthe1der/status/883349721489842176 Some of the responses took a dark turn. https://twitter.com/darth/status/883349152448495616 https://twitter.com/fMRI_guy/status/883349301979619329 Of course, someone made the obvious joke. https://twitter.com/CardinalBiggles/status/883351717487706112 But this was the most heartwarming. https://twitter.com/DueceWain/status/883350072926232576