It's a fangame made by Neweegee in GameMaker Studio! Based on Nintendo's Super Mario(one of my favorites).

Featuring custom graphics, New Super Mario Bros Style music(not much 'bah!' though) and new enemies and obstacles!
Some surprises await, too.

In the story, it has been 10 years since Mario's last adventure and a lot of things have changed. You get to play one stage and it's 4 rounds in this demo. Defeat enemies and collect coins to power up, giving you new abilities!

With Both of their own abilities, switch between Mario and new character Patty Ptooie to power up and beat the stage as fast as you can(once you know the stage, of course).


Controls
Up, Down, Left & Right(MOVE) = Climb, Duck, Move Left & Right
A(A) = Jump, Select
S(B) = Run
Shift(L) = (while standing)Pull Ground
C(R) = Attack(Power Level 2 or higher)
Enter(START) = (while standing)Switch Characters
Backspace(SELECT) = Change Camera mode

^ Those controls can be changed on the stage select menu by pressing Up or Down.

Ctrl = Power up!(Only when you're at Power Level 3)
Space = Switch screen mode
F2 = Reset the game instantly
Esc = End the game instantly

You can read the file that comes with the game to learn more about the gameplay

Click to enlarge.