5e follows the real world day-night cycle. When it's time for a long rest, everyone lies down and sleeps till morning. Keeping watch is optional, but depending our your DM, probably recommended.
5e sessions emulate the Blood War, with half the players as devils and half as demons. (The DM is an insane yugoloth archlord)
An essential part of your character is a plush toy and an adoption certificate.
Magic really works. This might sound like fun, but if the DM is polymorphed into a frog and there's a hungry, inquisitive cat around, it could all end in tears.
5e implements the Duke Nukem Forever gaming engine.
5e is secretly codenamed the Pulling Edition, containing heartfelt tributes to Patricia Pulling and containing "nothing she would disapprove of".
Players have to complete a scavenger hunt for each ability they want their PC to have. It's rumoured that you have to acquire a tram ticket, a photo of a 50-plus year old truck driver in Spandex, a Bob Wills '78 and a pompom signed by an NFL quarterback before your wizard can cast magic missile.