At their ages, most cooperative play is really just parallel play. That is, doing the same thing near each other, rather than sharing a single toy, or playing house together, for example. And this photo is a perfect example of their parallel-play friendship. These two get along fantastically with their own set of crayons and paper, or their own pile of Play-Doh and tools, or, in this case, their own bottle of bubbles.
This photo was entered into the I Heart Faces weekly photo challenge