Rob's Room: Sesame Street Watercolors by Jack Davis

Three original watercolor paintings by Jack Davis. These were used as Sherlock Hemlock’s Hidden Answer jigsaw puzzles from Educational Toys, Inc., 1971.  The first one has hidden S’s, the second has hidden shapes, and the third hidden numbers. (Via Raiders of the Lost tumblr)
Can you find all the hidden messages... err... hidden items, boys & girls?