First day of April

Yesterday, which was NOT the first day of April, Spencer had a friend over. He says to the friend, "Tomorrow is April Fools Day, I am going to start playing tricks on people today." My first thought was, "you can't do that, it's not in the spirit of April Fools." My next thought was, "how does my 6 year old know that tomorrow is April Fools Day AND how does he know what it is?" I know, funny that I didn't think of that first, but I didn't.
This morning, the boys were watching a show and I was changing the baby's diaper, sitting on the floor. Spencer says, very seriously, "Mom, I just saw a mouse." He was totally serious. I looked at his face, trying to get a reading from it, he was completely serious. I said, "Where did you see it?" Still not sure if he was kidding. He had a half serious, half smile on his face when he told me he saw it under the couch. The smile made me think that he was kidding. So, I said, "Really? or are you tricking me for April Fools Day." His face lights up and he says, again - very honestly, "Oh, I forgot that today was April Fools Day. Carter! There's a Star Wars guy behind you!" All day long he has been saying things like that, "Carter, there's a giant jelly bean behind you!" It's weird because although he has admitted that he didn't actually see a mouse, it was like that was the only normal thing he's said all day, AND I believe he really didn't remember that it was April Fools Day today. It all makes me wonder... did he really see a mouse? Something must have made him say that... what was it? So there you have it, the most perfect AFD trick, say something serious and follow it with off the wall comments all day, it will leave your victim feeling completely paranoid for the entire day... Wow! That boy is good.