Today's Thanksgiving Day (US) calendar entry reminds me that once upon a time there was a thought of producing occasional cards based on Common Errors in English Usage. The idea never got off the ground, maybe in part because of the difficulty of pulling it off for several different occasions.
But then again, there was "thankyou, thank you/thank-you," which I thought actually made a decent card. Here was the outside of the card I dreamed up:
Happy Thanksgiving (US) to you, and if you want to use this card yourself for your own thanking needs, here is a downloadable, printable, trimmable, foldable version (for a usable card, use two-sided printing; the crop marks will guide you to proper trimming and folding, and no, I am not available for tech support):
Thank You card—outside
Thank You card—inside