Ranma daisuki! Sayonara wa iwanaide!! - S1-E17
Revealing mistake: Ranma catches Shampoo, who drops the bottle she was holding. Ranma picks it up and it turns out it is a fake one, with a #666 label. When the bottle was falling off her hand, the label was #119. (00:10:50)
Shanpû no hangeki! Hissatsu shiatsuken wa mimo kokomo ubau - S1-E16
Revealing mistake: In his close-up when he grins at Ranma after his request to help him figure out what happened to Akane, Ryoga is drawn really obviously with the hair going under his eyebrows. (00:15:00)
