I think i'll call this trick "Early damage"

In stage 2 boss, you can hit it from behind, but you need to be hidden in the barrel. So you can start the bossfight, get in the barrel immediately, and as soon as Wally turns around, warp to the other barrel and beak his back from behind, and it will continue to go to the other barrel. I think it's possible to do it five times to shave some good seconds, plus, it's not that hard, so it might be a good thing to do in runs.

Here's an example of 1 early damage, knowing that 5 is surely possible:

BTW, I dunno why i'm posting this, this isn't even an active speedgame, but I think it's cool lol, it can save like 5 seconds

ooh awesome discovery, thanks for sharing :D