Are temporary tattoos (the decal-types that you press on to someone) melacha?
My instinct says they are melacha, but what av melacha do they fall under? Are they writing even if they don't contain meaningful letters or symbols? Are they dyeing?
If they are forbidden, is the prohibition rabbinic (since it is clearly temporary) or d'oraita?
I'm asking for the perspective of someone who does think using stickers to violate shabbas (that may not be a debated issue, but I feel that is a related issue nonetheless).