Tales from the Crypt/WMG

The Crypt Keeper is Rod Serling.
After he quit the Night Gallery and long after he was done taking people into the Twilight Zone, Rod Serling moved into a creepy mansion on a hill, died, and decided to continue telling creepy stories even after death in the crypt below the house. Due to the location, he took up the moniker of "The Crypt Keeper". For this to be true you would have to ignore the episode, "Lower Berth".

The Cryptkeeper is the same one from the Amicus movie of the 70's.
It's entirely possible that after a few decades of being undead, he began to rot a little bit. His personality change could also be explained away by the fact that his brain is rotting too, so he's gone a little funny. For this you would have to ignore Lower Berth again.

The Crypt Keeper plays on the tire swing hanging from the tree in his yard.
Why else would he have it there?

The stories are all true, but don't happen until the Crypt Keeper tells them.
In that way, he actually makes them reality. Thus making ol' Crypty a type of god.

Miguel Ferrer's character in As Ye Sow is the same guy from The Thing From The Grave.
Assuming that As Ye Sow happens first chronologically, it makes perfect sense that his assassin character from that episode would later start dating Terri Hatcher's character from The Thing From The Grave. His past as a killer would explain why he was so psycho in the latter ep and why he was so good at killing.