It is revealed here that witches can block fairy magic.
If Alden Bitterroot is indeed an ancestor of Denzel Crocker, that would mean Crocker has witch blood in him. It is unknown if he has "witch powers" like Bitterroot as he's never demonstrated them in the show.
Dale Dimm is apparently thought by many people to be a myth since there was apparently no actual proof he existed. This was changed when Timmy was able to take a picture of Dale Dimm and the rest of the Colonial people together holding a sign that welcomes people to Dimmsdale. This picture was then shown to A.J. as shown in Timmy's float.
This episode (along with its partner episode, Kung Timmy) rarely air in reruns for unknown reasons.
Apparently people in the present have always believed that Alden Bitteroot was a big muscular Pilgrim that got rid of actual witches and didn't realize he was just a Pilgrim version of Mr. Crocker until Timmy found out about that when he went back to when Dimmsdale was found.
The title of this episode is the exact same title of an episode of Scooby-Doo, Where Are You? Coincidentally, both involve witches.
Bitteroot is revealed to be a witch. Technically, male practitioners of magic are called warlocks, wizards, or sorcerers, so he should be called either one of those things.
Salem Witch Trials - The episode's plot is based on the Salem Witch Trails from 1692 to 1693; which was the chase of people supposedly being involved in witchcraft.
Dimmsdale is located in California, which wasn't settled until 1769. Also, during the year that Timmy and his godparents travel to (1665), California was under the control of the Spanish (from Spain) rather than the British (from England).
Also, California didn't become an official state until September 9th of 1850, and became a state largely because of the California Gold Rush (which happened from 1848 to 1855).
Alden Bitteroot: If he survives, he be'th human. If he drowns, HE IS A WITCH!
Alden Bitteroot: (after Timmy accuses him of being a witch and after the villagers grab Timmy by the arm) Doth art mad! Mad I say-eth!
Timmy: Oh, then, why don't your feet touch the ground? (Alden's feet are then shown floating in mid-air, causing the villagers to gasp and realize Alden is a witch. The villagers then release Timmy off-screen and he walks right beside where the mayor is)
Mayor: And may of us were quite perplexed about that?
Alden Bitteroot: Thou hast ruined my plan to take over-eth this town! (Alden activates his broom which causes storm clouds to appear and shoot green lightning on him. He then laughs for a bit and we then see his colonial hat change to a witch's hat. He is then shown surrounded by green lightning.)
Timmy: [after looking at Alden Bitterroot and a 21st century picture of him] So much for historical accuracy.
Although this episode premiered in 2003, it was produced in 2002 according to the credits.