Flat Zone 2 is Mr. Game and Watch's home stage on Smash 3DS, and is kinda sorta on Wii U as well. Flat Zone 2 is set inside a Game and Watch, transitioning between four different games. First up is Fire, a game where you have to escort Mr. Game and Watches out of a burning building and into an ambulance using a trampoline. You can be a horrible bastard and use the trampoline for yourself, letting a poor, innocent Mr. Game and Watch die, or at least get critically injured, just so you can get a boost. There's also some guy placing platforms everywhere. He's from the game Manhole. Yeah.
The stage will then transition to one of three other Game and Watch games. One of these is Oil Panic, a game where you have to get oil out of a leaking tank or something and get it into some angry customer's cars. You can attack the customers, but they will counterattack, causing you a good amount of damage. Another game included is Chef, a game where you have to bounce sausages up in the air to make sure they don't fall to the floor. And like in the other games, you can harm an innocent Mr. Game and Watch. Specifically, you can knock the chef out of the stage. He wasn't doing anything wrong. He was just trying to make a good meal. You bastard. The last of these is Lion, a game where you have to keep a lion in it's cage. In Smash, though, the lion-keepers are trying to keep you in the cage. Everybody hates this part because the fight becomes less of a fight and more of getting bounced around by the lion-keepers until your damage gets too high and you get KO'd. Hurray.
There's another game, Helmet, but that only appears in the Wii U version. Please understand.