The theme is "Pulling a rabbit out of a hat" (notice HARE coming out of each hat). Lemme know if you want the theme to be revealed in some way in the puzzle or if it's fine the way it is.
Fun crossword! I didn't spot the theme until I read your comment - I think you could definitely mention a "magic trick happening thrice in the grid" in the crossword note, or similar. Nice job getting those lovely long Down entries to work!