The hat could be made out of an Oreo and a Hershey's kiss. I believe the legs are pretzel sticks which are dipped in white/chocolate icing for the striped effect. The shoes could be made out of gumdrops that are shaped into shoes.
Add a little red food coloring to the marshmallows when making your basic crispy treats and stir until you get the desired pink color. Let the treats cool 10 minutes, cut out the hearts (about 35) and insert a lollipop stick in each.
Shamrock Pretzel Bites. On a parchment lined cookie sheet, bake pretzels with Hershey's kiss on top for 7 minutes at 200 degrees. Remove and immediately press three green M & M candies. When cool, use icing tip of green frosting to draw on the shamrock stems.