There is hardly any space in the bodies of heyokyay stick figures. Therefore, organs such as the heart or the stomach hang around outside the body.
The brain actually fits nicely into the head. But most of the time, it’s just not there, mentally and physically. Sometimes it gets into arguments with the heart about who’s being more irrational.
When it’s raining, all organs are folded and stowed away in the head. (That’s why the characters have such big heads.) Of course, every head can be opened at the top.