To do this, you need to go into your settings and change the date to either Christmas or Halloween. It doesn't matter which one you choose, because it still unlocks it. You can also wait for these holidays to come. Once you have done this, enter your game. When you get to the main menu, there should be a button that says holiday bonus. It will be unlocked now and you can choose between two different modes to play.
Secret Random Battle
First off, you will need to start your game. This secret can be accessed in the title screen or main menu. Swipe the screen a few times and a battle with a random level and four random characters will start. You will be able to play in it.
Stay Big or Small
This glitch will work on any map with any character. Become big or small by grabbing an orb with a + or - on it. Then jump kill yourself. You can become normal sized again by grabbing another orb.