Technically, making the effect of a Special Check Break Global Check negative instead of positive would make it enormously easier to pass (you need to roll higher than a negative number? well, gee golly, I dunno about that!). The flip ability is dastardly, though.

Actually, I believe that it applies only to check BONUSES, so the text of the check itself would never be altered... Now, if you had something that made someones Special Check Break Global Check effect higher, and then used Fairy Godfather on it, and then redirected it at yourself, THAT woudl do it, as long as you were raising the effect by more then its base.

Correction to my previous comment-- My assumption is that the Gangster Octopus/Fairy Gofather combo involved forcing the opponent to procure a negative-sided die, thus ripping apart time and space... Or possibly not. I was always more of an RPG person in ELotH:TES terms then a CCG person, so I may be quite wrong.