Mark came in with Doug, who was suffering from sunburn. However, Doug was more concerned about some white marks on his skin. House grabbed a syringe and used it to squirt water all over Doug. This ellicited a laugh from Mark and House asked Mark if his father liked to drink from brown bottles while he was on his boat. Mark nodded yes. House did a quick mental calculation and told Mark he would trade the syringe for the exact amount of change Mark was carrying. Mark handed over the change and House matched the coins perfectly with the white marks. Doug was a little upset, but House realized one of the quarters was Canadian and asked for his syringe back.