Crossword puzzle clue "hint to finishing this puzzle"

Hint to finishing this puzzle

Hint (and a hint to this puzzle's theme)

Mark that appears four times in this puzzle (hint: the baseball player who's the answer to this puzzle uses one, too)

Puzzle invented by Lewis Carroll (and a hint to this puzzle's theme)

Classic letter puzzle -- or, when parsed differently, a hint to three Down answers in this puzzle

You may have it if you clicked on several other links before finishing this puzzle

1937 Best Picture nominee (and what you might shout after finishing this puzzle)

"Congratulations on finishing this puzzle!"