Просто так!

​

This is an interesting combination of words because it can't be translated into English word for word. Просто means "just" while так can be translated as "so". However, the meaning of these two words together will change depending on the situation (context) they are used in. Such combinations of words are called idioms. One of the possible translations of просто так into English is "just because, for no particular reason". Sometimes we do good deeds for no particular reason, просто так. Enjoy this cartoon now :)