75m is based on the second level of the same name from the classic Donkey Kong arcade game. It's been in the Super Smash Bros. series since Brawl.
Unofficially the original Donkey Kong is Crankey Kong now, so Mario gets to meet him again.
But anyway, like the real Donkey Kong game, watch out for these things, they'll hit you hard.
Though I will admit, it's an awkward stage to fight on. I know the pro players probably hate this stage with a passion. I don't blame them.