On WCAU-DT in Philadelphia, they switched by mistake at 9:30P (in the middle of West Wing) to the west coast NBC feed showing the NBC Nightly News. I had already seen that episode of West Wing but I would have been real annoyed if I was watching it.
I noticed this while surfing around during a King of Queens commercial break. I pointed out the WCAU-DT mistake to my wife. She can't believe the local affiliates can screw up like this.
On Tuesday night, WPVI-DT, the local ABC affiliate didn't switch over to the local news feed at 11P so we were treated to the first 5 minutes of the west coast HD feed of 8 Simple Rules.