All of this info comes from Tales from the Crypt: The Official Archives by Digby Diehl:
Tales was created by five big-time producers and directors: Richard Donner, Joel Silver, Robert Zemeckis, Walter Hill and David Giler. All of them read EC comics as kids, and they wanted to translate the stories to television. They decided the vignettes should have a common thread. Remembering horror hosts like Alfred Hitchcock and Vampira, they decided the show needed a host, so they brought in the Crypt Keeper, one of the three narrators used in the EC stories. The other two were the Vault Keeper and the Old Witch. Oh, how I wish they’d made puppets of them, as well!
Kevin Yagher was in charge of CK’s production. He got the job by pure accident. Joel Silver had gone to his storage garage to pick up a few things, and Yagher happened to be there at the same time. Silver looked over and saw this guy with all sorts of monsters and puppets in his garage, so they started talking. Yagher had designed Chucky, so he seemed perfect for the job.
Yagher did some prototype sketches and clay mockups. The originals looked much like the character from the comics, but he seemed too busy. The team started taking out parts–hair, lips, eyelids–until he looked like the final CK with a nose. Yagher said they went through 6 or 7 noses (which Diehl describes as a demented Mr. Potato Head session), when they finally realized that he didn’t need a nose.
John Kassir was cast for the voice. The voice he chose was a mix of Hitchcock, Rod Serling, and the Wicked Witch of the West. In the early episodes, the CK is quite raspy. He didn’t develop his later, shrill tone until late in the first season. The reason was because doing the voice was hard on Kassir’s vocal cords.
The CK kept his traditional demeanor and robes for the first two seasons. In the third season, he became more playful. He was often in costume, and his humor was cheekier. When dressed as a famous actor or character, Kassir did a top-notch job of voicing the Crypt Keeper imitating another person. If you can, find a video of the CK doing his Godfather or Forrest Gump impressions.
Now the technical stuff! CK was built by a team of 8 people from Kevin Yagher’s studio, and it took 6 people to operate him. Seated below the CK, Van Snowden operated the head and body. Seated behind him, Charles Lutkus operated the arms and hands. The arms were done Henson-style, half arms with straps that attached to the puppeteer’s hands. In scenes where the legs were visible, a third puppeteer was seated below and toward the front of the CK. No name was given for this person, so I’m guessing no single person did this job. You didn’t see the CK’s legs very often.
Four puppeteers worked the face, which was controlled with 27 servo motors. Needless to say, Crypt Keeper’s head weighed a ton. They worked to a prerecording of Kassir’s voice work. Brock Winkless worked the jaw and most of the mouth movements. A device strapped to his head captured his own jaw movements, which controlled the puppet’s jaw. At the same time, he worked a four-stick console that operated four points on the puppet’s mouth, doing most of the lip sync. The points he worked were toward the center, one by each canine tooth. David Stinnett worked the corners of the mouth, making the puppet smile and working lip sync on sounds that cause the corners to pull back–the letters E, B, and T. Winkless and Stinnett had a really tough job! The servo motors weren’t powerful enough to pull the corners of the mouth into a smile, so these were operated manually using ten-foot cables. Erik Schaper operated the cheeks and nostrils with four joysticks, while Mecki Heussen operated the eyes and eyelids.
The Crypt Keeper was made with a foam rubber that rotted very quickly. How appropriate! I know foam rubber doesn’t last forever, but it sounds like his decomposed unusually fast. HBO runs short seasons, so he worked for a couple months each year. During the rest of the year, a team would clean him up and remake his soft parts. So in a way, you see a different Crypt Keeper each season.