Plot holes: At the end of series five Rachel and Ross get drunk in Las Vegas because Ross has used a permanent marker pen on Rachel’s face, which they are told by the manufacturers cannot be removed and will only fade with time. She uses the same pen on him. At the beginning of series six they wake up together with all the markings on their faces but when they arrive downstairs for breakfast all the markings have been washed off completely. This is a major plot hole because if the markings were washable they would never have gotten drunk together and ended up marrying.
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