And it doesn't involve explosions, dirt, or noise...

Every night, about 10 minutes after they go to bed, both of the boys wander out of their room down the hall to the bathroom to get a drink of water.  They have special cups in there with their names on it that they can use.   They each grab their mug, and before they take a drink, they clink their cups together, like they're "toasting."

Matt and I watched them do this several nights in a rom (we can see them from our bedroom) before we asked what they're doing.

Hobbes's response: "We're toasting to our good friendship."

Makes up for all the arguments during the day...