There was a reason why Matt Smith, Karen Gillan and Arthur Darvill had such great chemistry: because the trio were as good as friends behind the scenes as the Doctor, Amy and Rory were on-screen.
This doesn't seem to have changed either. And judging from the video Karen Gillan posted to her Instagram account, she still misses the good old days of clowning around on set – even if things were apparently super weird.
Yes, that is a video of Karen Gillan resting on a table while Arthur Darvil and what-sounds-like Matt Smith serenade her to the tune of O Little Town of Bethlehem. We're particularly big fans of Gillan's faux-quivering. They don't pay these guys the big bucks for nothing.