Cut characters:

• Ice Climbers
• Lucas
• Ivysaur
• Squirtle
• Snake
• Wolf

It doesn't have to be someone working for ESRB. The rumored story is that it was an employee for Nintendo. A tester, who went on to do other things and is no longer an employee there.

I guess the biggest reason why this leak seems real is because the stage select screen contains a stage which we had never seen before. And after this leak hit the internet, this very stage was shown in a Famitsu scan.

Yes it was the Tomodachi Life stage that was shown earlier. But what was shown earlier is what you see to the left in that image. However, the thumbnail image from the leak's character select screen shows a room of the Tomodachi Life stage that we hadn't seen before. Until a few days later when that exact room was shown in a Famitsu scan (bottom right in the image), and from a different angle.

Yeah the order of the character select screen looks really off to me too. However, I heard an explanation for it on Gameexplain's videoanalysis ( https://www.youtube.com/watch?v=wo-1cx0wXgc ) that makes sense.
I forget the exact details, but basically they mentioned how the positioning of the slots on the character select screen has been jumbled in previous games before unlocking the full roster. They said something like "Pikachu appeared between Bowser and Yoshi, which made no sense, until you unlocked the rest of the cast."
And they point out how this game will supposedly have DLC characters since that info came from the same people who leaked the pictures. So they're saying that perhaps the order of the slots will change back to a more logical order once you get those characters, like with the previous games.

And yeah, Sakurai has teased and trolled about Ridley for quite a while. I'm interested in Duck Hunt dog though. Really like the artwork for him in the pcture. I just hope he's a unique character and not an Olimar clone.
The biggest surprise for me is that Bayonetta isn't in the game in this case. I thought she might be a Zero Suit Samus clone, since Zero Suit Samus got those new heels that give her movements a boosts, and Bayonetta has guns for heels which can do the same, and the two share similar poses and movements.

Yeah, there's always the possibility of more characters missing or being added later. Ridley is one of the most requested ones. But would he have to be shrunk down in size in that case? I've only seen him in Super Metroid. But there I think he was around 3 times the size of Samus?
The dog does look very different. I like his new look though. Well it's more the bird's look that I like, in combination with him. But I would also like an alt costume for his original look since it's so classic.
I can just imagine him giggling on the screen after zapping the other players or birds with a zap gun as his Final Smash. Hehe

Yeah you're tright about that. Bowser and DK are already pretty big, and have appeared in different sizes in different games.

And the reason I mentioned Duck Hunt dog possibly being an Olimar clone is because, I didn't know about this before, but apparently there's a patch for Project M where Olimar's character model is replaced with the dog, and the Pikmin's are replaced with duck skins. The character still works the same as Olimar though. I hope that's not going to be the case here. Like you said, there's not much to the dog in his game, so Sakurai would have to come up with original moves for him, unless he just makes him an Olimar clone.