NBA players get pats on the back if they register double-doubles. They make headlines if they register triple-doubles.
Rarely does anyone accomplish a quadruple-double.
Only four players since the 1973-74 season have finished a game with a quadruple-double, which requires a player to finish in double figures in points, rebounds, assists, blocks and/or steals (any four).
There likely would have been more before 1973-74, but that's when records were first kept for steals and blocks. The last guy to do it was David Robinson in 1994; Nate Thurmond recorded the first in 1974.
RE: Which of these unusual events was the most improbable?