Okay. Falcon is like Diddy, but much worse. And I don't mean this in a good way, I mean he's worse for us to face. In fact, he's probably our worst MU in the game.
Every zoning character's weakness is getting rushed down, and Pacman is no exception. That being said, Falcon is the most rushdown oriented character in the game. I did not even start on why the MU is hard and what we can/cannot do, and it's already looking pretty bad.
Falcon is extremely fast, which means it's hard to keep him away. You can't run away. You won't have time to charge Fruits as you please and fool around. He's not as fast as Sonic, but Sonic usually either jumps after his approach, or retreats if he fails to connect a hit. Fox is fast, yes, but against Pac he should be playing using his reflector a lot (at a distance), and he's designed to be more of a ''punish things by being fast'' character, so even if he can play more agressively, it's still a Fox. Falcon is not like that, he's a ''go in and keep pressuring'' kind of character. You have to approach this MU with the same mindset you should have in doubles: every second is precious, so be productive.
Now, another pretty bad thing is that Falcon can spike reliably. The offstage play was one of our advantages against Diddy, but being offstage for too long is dangerous with Falcon. Try to get back to the ledge as soon as possible, even if this means you have to face Falcon. Also, whilst not ideal, Falcon's recovery is arguably better than Diddy, but it's still gimpable. If YOU are the one doing the edge guarding, you can go offstage if you keep it safe, but be wary of the UpB.
Falcon doesn't have a reflector (we would have been super ****ed, honestly), so use this to your advantage. If you have a moment, charge a fruit, he can't really do anything against them. Same goes for the Hydrants, don't hesitate to launch them, but it might be useful to keep them for the water, depending on the situation. The Trampoline is amazing, because it means he can't approach on the ground, abuse that. In this MU, your win condition is really going to be B moves spamming more than anything else.
Neutral air is great. It comes out really fast, so it can get you out of troublesome situations. If you feel like you are pressured too much in the air, this will be your go-to aerial due to it having a long-lasting hitbox all around. Even if our opinions differ on the utility of the move (you should check out and participate in
this thread, if you haven't already), we can all agree that Fair is a nice spacing tool, and it's also a fast one, so it's also one of your most useful options here. On the ground, Ftilt is good, as well as Dtilt and Jab. Anything fast, really. Try to use less than usual the moves that have more ending lag. Remember: this MU is all about spacing properly, more than it is about doing damage.
Falcon is indeed great at pressuring people, but he still can't go in carelessly. Think of it as another type of Marth/Lucina; he has to approach safely. If he makes a mistake, your punish game has to be on point, and it's a good opportunity to gain momentum.
Comboing with stuff like Fruits (Cherry) and aerials (Fair) is an option. Pacman is quite versatile in his combos, so you can do a lot.
I know all I said is pessimistic (let's be honest, it is an hard MU), but that's also the mentality you need to have. Even if it isn't, you should be playing like your stock depends on it. Even at low percents, you should be playing like you cannot let him take an advantage by doing a mistake or an unsafe move.
Platforms don't really add anything since Falcon's Uair is so good, and it blocks your Hydrants/hinders your Fruits. Try to go Omega if you can.
Always move. There's no reason to stay in one place, it only makes Falcon's life easier. If he wants to hit you make him work for it.
I give this a 25:75 or a 30:70 Falcon, at the moment, but I hope we can somewhat push it up a bit by finding ways to deal with him. You can argue that since we're a zoning character, we have an advantage on Falcon (as we did with Diddy), but I personally have trouble with him. I hope everyone's not like that. After all, Pacman doesn't need a body because he bodies people. Let's keep this true.
I'll be doing more testing and research on my side to come up with concrete options, but I feel like we can get a good discussion going from what I've said.
These are two videos of somewhat high level matches of Pacmans against Falcons (I couldn't find more, which tells a lot about the MU), it's always good to watch to see what they do right and wrong:
/watch?v=c2S_tUI-Ax8
/watch?v=pzR7oTltzo8