What does Thor say to Hulk to calm him down?

What does Thor say to Hulk to calm him down? When Thor is trying to calm down hulk he starts singing a little mantra “Sun’s getting real low, sun’s going down.” While Thor doing this by itself is pretty funny given the context, I forgot where this originated.

When Thor is trying to calm down hulk he starts singing a little mantra “Sun’s getting real low, sun’s going down.” While Thor doing this by itself is pretty funny given the context, I forgot where this originated.