I've heard that. But the "undead" what's with that. If one is not alive, then one has no way of moving as there is no way for the muscles to contract. Also no brain activity. If the drink blood to "unlive" how do metabolize it? If they have no muscle control the blood will eventually leak out their butt. Messy

Also, how does one physically grow extra long teeth then later have them shrink.
It's just crazy.
This all aligns itself with credibility in movies where cars collide with a bus and the bus flies though the air
If we don't count our blessings
We are just wasting our time