Be Afraid of the Dark (2) - S3-E12
Plot hole: When the Corrodium Beam is shut down, there is a brief scene of the sky clearing at Mount Rushmore. But on the cliff face all four heads are seen, whereas the head of Theodore Roosevelt got crumbled in "Secrets," and it's too far forward to have been carved into the mountain face, in place (and same position) of the old head, yet again.
The Kidney Stays in the Picture - S7-E16
Plot hole: It is explicitly stated in this episode that Hayley was conceived in 1996. While normal for shows without character aging to change birth years to benefit the plot, this move was premature. Hayley's permanent age is stated as 18, and this episode implies that in 2012 she would be much younger than this. The whole plot centres around her being legally able to drink in a bar, so this is a pretty big mistake.
