I made a quick and crappy test run of the first level of Mischief Makers using solely frame advance if anyone cares enough to see it. It has a few obvious flaws, of course, since this is really only my second or third attempt ever at doing any sort of TAS whatsoever, but it does show how quickly the game can potentially move.
http://cupofdirt.net/poop/mmt1b.m64
The "S Rank Guide" FAQ writer on GameFAQs says his best time is nearly a second faster than mine, so there's at least a second of improvement (out of a 9 second level) in there. For example, the places I decide to jump are kind of weird, I'm not too quick at grabbing the guy on the shrine and turning around, and I couldn't make it up to the eagle wing without boosting before throwing the Clancer, which the guide writer says should be possible without boosting. Maybe I just didn't try enough options. Anyway, there you have it...!