Since the the older kids had a field trip I just had the K-2 class. It was St. Patrick's week, which is one of my favorite holidays, and green is my favorite color too;-)
An impromptu idea was to make shamrocks out of hearts, which the kids are pretty good at making. The great thing is that the fold in the heart is perfect for maing it look 3-D. I had the kids make a bunch of different green hearts as well as some real simple squares of green and brown for a "leprechaun" hat that the shamrocks would be sprouting from. All this got pasted down, with the idea that the three hearts pasted together made a shamrock and only half the heart was glued so that the other part stuck off the paper to give it a lively look.
The kids did a fine job on these and they were dead simple to get organized and make.