A 6 year old cleaning spree

Chandler & Carter came home from soccer practice tonight. As soon as Chandler walked in the door, he went to the living room & started picking up all his toys he played with today. I almost always have to tell them both to clean up when they are done. But I was thinking, "wow, he's picking up without me asking." So then I'm fixing supper & hear him in his room. Our neighbor came over today & they were playing camping in the boys bedroom, so it was kind of messy. I went in there & he was cleaning his room. He ate supper pretty quick... highly unusual... and started cleaning again. He picked up Carter's stuff... toys, soccer cleats & socks, then went back to his room & finished cleaning in there. He made up his bed then proceeded back to the living room & started picking up Kensley's toys & moving them to the corner. THEN.. he got out the vacuum cleaner & started vacuuming the house. At this point, I'm wondering what the hidden agenda is with him. He's cleaned some, but never the whole house for this long. Next, he went in our bedroom & picked up the clothes on the bed & put them in the basket, cleaned up the shoes outside our closet & vacuumed in there. THEN... he proceeds to cleaning the bathroom. Clearing off the counter & wiping it down & straightening the shelf above the toilet & I think I even heard him spraying something & cleaning the tub. About 45 min later, I finally stopped him & asked why he was cleaning so much. He said he thought about it all the way home & wanted to do this for me because he knew it would make me happy. Awwww how sweet! I rewarded him by letting him move all his rocks to the happy jar, therefore he gets a reward of doing whatever he wants. He asked to go to the fire department. I guess we'll be making a trip there tomorrow.