Sure! Here's an example of a simple game combining elements from Mario and Sonic using JavaScript:
In this game, you control a blue square player using the arrow keys. Press the up arrow key to make the player jump, right arrow key to move right, and left arrow key to move left. The player is subject to gravity and will collide with the boundaries of the canvas.
Of course, this is a very basic example, but you can customize and expand upon it to create your own unique Mario & Sonic game using JavaScript!