"Favre completed his first official NFL pass—to himself—on September 13, 1992, in a game against the Tampa Bay Buccaneers. Starting the game in the second half, Favre's pass attempt was deflected by Ray Seals. Favre caught the deflection, but went down for a loss of 7 yards."
http://en.wikipedia.org/wiki/Brett_Favre
So I guess the INT in 1991 doesn't count as an official pass then