This is the beginning of the code that is executed for game mode 10 (the black period between fadeout from the OW and Mario Start).
$0096A5 is which Layer 1 tile on the overworld will prevent the "Mario Start!" from appearing if the player is on it. (Default is $56, the Yoshi's House tile.)
Change $0096A6 to EA EA to make MARIO START! appear on the Yoshi's house OW tile number, or to 80 03 to make the MARIO START! never appear.