I was surprised this activity worked as well as it did! I thought that the watercolors might leak under the stickers, or that the stickers would make trouble when we peeled them off, but neither really caused a problem. (A little bit of leaking, but that's because the girls used buckets of water! :-)
We did try doing it with regular paper (instead of watercolor paper) and that did NOT work (ripping and leaking ). Also, we only used foam stickers. I'm not sure if regular, flat stickers would work or not. Has anyboday tried that? It's Playtime!