New art canvas

E has found a new canvas for drawing with markers:  herself, especially her belly.  She lifted her shirt up for me today and said "drawing!" while showing off a belly with pink marker all over it.  It was funny until bath time when I tried to get it off - it was a little difficult, even though the markers are labeled "washable."  Why can't she just draw on paper like a normal child?  Or the furniture?  Or even her limbs instead of her tummy?!?!?  *sigh*