Something to the effect of someone trying to make phone calls from Notre Dame, and a call to heaven only costing $0.25 or something because from Notre Dame to heaven "it's a local call." It was a bad joke told only once, but different people not knowing it had already been posted kept posting this very lame joke.
Then...as I remember, people kept doing to same thing when Davie was coach with this joke about "a mysterious white podwer" at Notre Dame practices that was later determined to be the goal line (har har har). We started replying "it's a local call" as if to say, "thanks, that's only been posted 562 times already."
Now when somebody is way out of the loop and posts something very old that pretty much everybody has already seen, "it's a local call." I think the idea is to read the board a little closely before slapping posts at the top. We all have the internet too.