Dash Drop (aka "Isai Drop") - When you hit the platform, if you hit left or right, your character will start to move and negate the landing animation, thus enabling you to drop through the platform immediately.


Shield Drop - Similarly, if you shield right as you land, you can slightly tap down to drop out of shield immediately. This is much harder than the Dash Drop, so you should only use it when you're already forced to shield on a platform.


No-Impact Drop - If you jump at a platform low enough, you won't actually enter your landing animation, and therefore can do anything such as drop through right away. This only works if you're approaching the platform from below, or just dropped through the platform. I've seen players like Bum using this as a mindgame, so I dub this one "Bum Dropping," mostly because that sounds awesome.


Waveland Drop - If instead of hitting the platform, you instead waveland (in any direciton), you won't have to deal with landing lag, and will be able to perform any move from there, like dropping through the platform.


PC Jump Drop - Essentially, if you midair below a platform at a point where you can land on it, you'll either go high enough to impact land on the platform (seen in the Normal Platform Drop), or go low enough that you'll just wind up on the platform without impacting (seen in the No-Impact Drop). If you happen to midair on the one frame that divides these two, you'll just pop up the platform immediately, and have no lag at all. Nifty, but mostly it's a flash mindgame - essentially an advanced version of the No-Impact Drop