Usually when the timetable goes out of the window, Northern also do the skip stop stunt. The last service that did that was a service to Man Vic via Brighouse that was running really late. From Leeds it ran straight to Brighouse then resumed its normal service pattern, saved somewhere in the region of 10 minutes. The poor sods who wanted stations in between were told to change at Brighouse and catch the train back.
I was once on the 07:07 Clitheroe to Manchester Vic, which got delayed at Whalley due to a Train Fault. There was some sort of coupling issue between the 153+142 combo. I seem to remember it starting its journey 5-10 minutes late at Clitheroe, but by the time it got to Blackburn, it was 30 minutes late, by which time it was running in the path of (and delaying) the 07:40 ex Clitheroe.
It was decided to run non stop from Blackburn, to Manchester Victoria.
Before I had boarded the train, I had seen on Northern Rail's website that they were planning on doing this, but I hadn't had chance to ask the Conductor, as he was busy selling tickets etc.
It became apparent that the Conductor wasn't aware of the planned non-stopping, as he only knew of the intention, when the station staff at Blackburn specifically advised on the PA, that passengers must not board, unless wishing to travel to Manchester. The Conductor therefore made a PA on the train, so people for intermediate stations could leave, and walked through the train.
I had originally intended to get the 07:40, but when I realised about the 07:07 ex Clitheroe being delayed, I knew it would have a knock on effect on the 07:40, which it did. I also saw how overcrowded the stations platforms at Darwen and Bromley Cross were. No doubt people there would've been surprised that the train didn't stop, despite the driver sounding the horn to warn them.
The service usually forms the 08:29 Man Vic to Blackburn/09:31 Blackburn to Man Vic, but presumably went to Newton Heath for the problem to be looked at in more detail etc.