This is one of those things. They were fighting over The Girlchick's stroller for her baby dolls. But they would take turns pushing each other around in it. I guess it worked for them since they were both "doing" something, either riding or pushing.
What I also find funny about the above video - watch Thing 2 (riding) at the very end of the video shake his head yes to his brother! It's something he just started to do - nod yes when we ask him if he wants something. It's the first time I have seen him do it to his brother - like come on, I still want to ride.
Here is Thing 2 pushing Thing 1. He has a little more muscle and bulk to put into it so he goes a little faster and can turn it.