The bathroom in Leonard and Sheldons [4A|apartment] is just down a small hallway from the living room. The room has a few superhero posters and a poster of the periodic table of elements on the walls (0317). The shower curtain is decorated with the periodic table (0101). Sheldon mentions to Penny that the tub has adhesive stickers on it of ducks holding umbrellas to prevent falls (0308).
Penny's bathroom is located on the other side of her bedroom from the living room in her apartment (0302, 0315). The walls are pale purple above white tile. Her shower curtain is blue. Penny's tub is sorely lacking in adhesive ducks (0308).