Here's a story from long ago. 

Back in the 60's I was a young F/E on the 707 flying a trip from JFK to Paris.  It was a nice evening as we headed east and I was busy doing fuel balance and paper work.  We were in cruise when the plane started a bank to the right.  The captain disconnected the auto pilot and leveled the plane.  The problem was the captain's horizon failed and the auto pilot did not disconnect and started to bank with the sick horizon instrument.  This meant the plane would have to be "hand" flown the rest of the trip since the auto pilot only worked off the captain's horizon.

After talking about the situation I suggested that I go down into the E&E compartment and swap the F/O's horizon for the captain's position and then the auto pilot would be able to work again.  Good idea said the captain!  So I opened the floor hatch behind the captain's chair and went down into the compartment under the cockpit where all the electronics were. Because there would be a short time that both horizons would be inoperative, we discussed the pilots would have to use the stand-by horizon.  Okay, down I went into the E&E compartment and found the two horizon gyros.  I disconnected the captain's horizon first and then disconnected the F/O's.  Oh no! - the two cannon plugs were different!!!  It was then that I noticed the sign... ATTENTION - DO NOT SWITCH GYROS!  :o

Quickly I reconnected both horizons to the proper plugs and and started back up into the cockpit. When I crawled up from the E&E compartment the two pilots were saying "You da man, you da man!"  It was then that I saw that both horizons were working just fine!

Should I have told them what happened or just take the praise?  ::)

As they would say... "flying is hours and hours of shear boredom punctuated by stark terror!"

Yes, I told them what I did in the E&E compartment.   ;)