Minecraft: Java Edition, since pistons arrived in 2011. Players have reported this to Mojang's bug tracker over 800 times (824 reports closed as duplicates of MC-108), with titles like "Pistons being powered by nothing." The report's own steps: a piston, a block on top, another block beside that, a lever on it. Flip the lever on and nothing happens. Set a block next to the piston and it fires. Flip the lever off and it stays out. Mojang closed MC-108 in 2013 as "Works As Intended".

The game's code says why. A piston doesn't watch for power: it only checks when it's placed or when a block right next to it changes. And when it checks, it also looks around the space above it, as if it were two blocks tall, the same two-block question a door asks. Dispensers and droppers ask it too. So the lever's block, up there, counts as power, but the lever's flip only updates the blocks around it, so the piston keeps its old answer until your block lands beside it. Players call it quasi-connectivity. Bedrock Edition's pistons don't do it.

As Nathan Adams (Dinnerbone) of Mojang put it in 2013: "Pistons can (and have always been able to) be powered from two blocks above."

The baby zombie riding a chicken in the back is a real rare sight: in the game's code (26.3), 1 zombie in 20 spawns as a baby, and about 1 baby in 20 comes riding a chicken.

The plaza, the piston, the lever, the door, the player and the animals in this film are our own simplified designs, built in code; the rule runs as the game's code has it.

Which redstone mystery should we cut open next?

Sources: Minecraft: Java Edition 26.3 and Beta 1.7.3, the game's code (PistonBaseBlock, DoorBlock, DispenserBlock, LeverBlock, Zombie), read with javap, Beta 1.7.3 also in the MCP and Project Poseidon decompiles. Mojang's bug tracker: MC-108 and MCPE-14664. Nathan Adams (Dinnerbone) on Twitter, 17 March 2013.
Not an official Minecraft video. Not approved by or associated with Mojang or Microsoft.
Sounds and music: our own, made in code.