I ran the command /fill x y z x2 y2 z2 minecraft:aracia_stairs[waterlogged=true,half=top]

Relatable to the skeleton slab glitch MC-120898 the skeletons will speedily run on stairs when provoking something. When not provoking something a skeleton will spin in place.

Zombies will spin in place as long as you do not move. Which gives some nice insight into how the zombie might work. Spiders have the same effect. Yes, spiders are not undead, but I felt like it was needed.