Pac-Maze (or PAC-MAZE as it's labelled in-game) is PAC-MAN's home stage on Smash 3DS. Unlike PAC-LAND, this stage is based on the PAC-MAN that everyone knows and loves. Also unlike PAC-LAND, it's actually good.
In this stage, everyone is PAC-MAN. Mario is PAC-MAN. Ness is PAC-MAN. YOU ARE PAC-MAN. I don't mean that in a literal sense (unless you are PAC-MAN). I mean that everyone can eat all those pellets and stuff. When you eat 100 pellets, you can eat one of the big pellets. And then you can eat the ghosts. It's kinda weird to visualize someone like Shulk eating ghosts. But it happens in the PAC-MAZE. Yep.
PAC-MAZE is also unique in that it's the only third-party stage to be 3DS-exclusive. While Sonic gets his Brawl stage and Mega Man has the same stage as the Wii U version Pac is the only third-party to get two new stages. This has nothing to do with Namco developing the game. Honestly, guys.