So on Saturday I thought I had a roll of Kodak Tmax 100 loaded in my Rolleiflex. I was shooting it at EI 50 to try a technique I had heard about. When I finished the roll and unloaded the camera I found to my horror that it had been a roll of Tmax 400, thus I had overexposed by 3 stops. I did some research/guesswork, and tried developing it in Pyrocat HD developer for 10 minutes and I got very usable negatives. When I mixed up the Pyrocat HD solution it turned bright green, which I have not seen before, but it still worked!