I bumped this to show Ryoko's discovery about invincible body parts. I quoted because I couldn't have explained it better myself.
I figure this would be useful for people across the board.
As you may know if you ever played with hitbox bubble mode in Melee, an appreciable number of attacks and actions have selected body parts invulnerable (actually, intangible) during execution. This essentially gives some moves more effective range and priority by temporarily disabling one or more of a charcter's hurtboxes from being hittable by other hitboxes. This same mechanic exists in Brawl and has been sitting rather obviously in PSA, although it is currently not in the list of premade events.
Each unique "event" in a PSA line has an 8-digit code. PSA has a premade list of events in plain English for our convenience, but is still using an 8 digit code that is particular to an event if you look at the text boxes while scrolling through them. The box next to the OK/Cancel button can be used to call upon an event manually via entering the 8-digit code.
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The 8-digit code for editing a "Bone Collision" is 06080200. Upon entering this line, you will see the numerical code itself and not a text-named event as it is not recognized by PSA's premade list of events. The line will appear as such with 2 parameters to edit, "06080200: 0-XX, 0-Y" where XX is the bone of interest, and Y is the type of body collision. I personally have not seen any Y values set to anything other than 2, which is the intangible bone collision.
06060100: 0-0, is the command that resets all bone collisions to normal. One can also reuse the Bone Collision code and set parameter 2 to a normal bone collision to revert individual bones. These should be used in conjunction with Synchronous/Asynchronous Timers just like offensive collisions.
Example attacks that can be observed in PSA of having these lines of code are Zelda/Sheik's Dsmash, Peach's Usmash/utilt, Fox and Falco's Usmash and Dsmash, etc.
Here are some screenshots of Melee with a couple of Peach's moves that exhibited this property, seen clearly through the game's debug mode:
Here's a really old image of "bone" Peach in Melee, doing her Usmash for reference of this phenomenon for those not in the know. If anyone remembers the futility of trying to attack Peach from above while she uses Usmash, this is why.