I believe there is NO theme but there is a reason for this. Its to promote new programmers into "releasing" games. The theme is just "goofy". If the game you make IS indeed goofy then it fits. Have a player animation go wrong, have your sprite flip the wrong way, have collision shapes the wrong way or even make them visible to the player. Make enemies run away from the player for a second and then come back. Whatever makes you happy can be posted.
Its to make new devs and programmers comfortable with promoting their games even WAY before they are 100% bug free.
I still to this day have not sat and coded a game without having 50+ bugs during it. Ive been making games for 2 years now.
the theme doesnt exist for a reason.
Happy coding!