Ages and ages ago when my brother and I were playing through Pokemon Red and Blue, we were working to get all 150 LEGITIMATELY WITH OUT CHEATING.
We got 147 on Red. The three remaining Pokemon were Bulbasaur, Ivysaur, and Venusaur. We decided to erase our file on blue so we could start from the beginning and get a bulbasaur.
Deleted the file on blue, got bulbasaur, got ready to trade. He pulled out Red, turned on his gamebody and... the save file was gone. The save ram battery died; our copy of Red could never keep a save file after that.