This will display an 8x8 sprite tile at the top or bottom of the screen when Mario goes offscreen, at his X position. This way, the player can tell where he is even though they can't see him.
Note: due to the order of how sprite graphical data is handled, this code only works in level ASM, not game mode ASM. To do the latter, you will have to manually add a hijack to the game mode (following the OAM clear call at $00A295).
Tried inserting this with UberASM Tool, nothing appeared when Mario was off-screen. Then I converted any 4 digit addresses in the code to what they should be for SA-1 to see if that was the issue, still nothing appeared. Am I missing something?
Edit: Got it. Just didn't have to update the oamIndex address, convert all other 4 digit addresses to be SA-1 compatible. I know it says not to but it's in the same number range as other addresses that need to be converted to work with SA-1 so I just figured...