An easy (and cheap) way to make bath time, day or night, a little more fun is to make bath finger paint.
I let Charis help mix it together using measuring spoons. The measurements don't have to be exact. I add more or less of any ingredient to get the consistency of finger paint.
1 T cornstarch
2 T liquid soap (shampoo, body wash, etc)
Mix cornstarch and soap together. I usually double or triple the recipe. Then add a few drops of food coloring to get the desired color. Last time I did it I did 2 T cornstarch and 3 of soap and it turned out fine.
So far it hasn't stained anything and washes off the walls perfectly. Great time to work on colors or cause and effect from mixing colors!