After the test marketing of the original "Thanks!" Card in Indianapolis during the summer of 2009, the "test" provided the marketing department that the wording "Thanks!" wasn't a sincere heading on the card, but the replacement of "Thank you" was. The coffee cup also changed with an added saucer. Other minor changes, including a different colored reverse was changed.
The other occasion Cards include "Happy Birthday" and "Congratulations", all released on May 4th, 2010.
These occasion Cards are considered "core" issues, as they've been readily available, including at various retailers as card hangers.