Tip: When determining a time limit, remember that players won't be as familiar with the level as you are. If you normally complete the level with the timer around 100, others might run out of time on their first try.
A disassembly of SMW's Spiny (sprite 13). It can be configured to face the player while falling from a ledge and move faster (SMB1 behavior) depending on the extra bit and extra property byte 1, respectively.
This is the most inaccurated dissasembly I have ever seen in my life, as more than half of the code is made up by the autor, which by itself it's not bad, but it shouldn't be marked as a dissasembly, in my opinion. In any case, if you are to insert it in your hack, be warned: it won't behave exactly like the original spiny, especially on slopes.