Where does he get this stuff?

We had macaroni and cheese for dinner tonight because Tim has to work and it's just the boys and I and that's what Collin wanted. When I went downstairs to get the box of mac and cheese the boys were playing quite happily in the living room with Collin's trains. In the 45 seconds it took me to run down, grab the mac and cheese and run back up something happened and Nick was crying. I scooped him up and said "What's wrong Nick-Nick?" Like he's going to answer me, but Collin piped up with "Nick cracked his noggin on the train tracks!". Seriously? Cracked his noggin? I asked him if that was what he said and he told me it was. I have no idea where he learned such a thing but it was too funny. I just couldn't contain myself and burst out laughing. Nick was perfectly fine by the way. Whether or not he actually "cracked his noggin", the train tracks are thin and plastic so he couldn't have really hurt himself. I think he just wanted to be held. Then as we were eating dinner I asked Collin if he was going to get a bath with Nick-Nick. He told me he was and then "the Nickster will got to bed and I can watch Henry!" I don't think I've called Nick the Nickster but I suppose anything is possible. Collin must have heard it somewhere. It cracks me up that he refers to his brother as "the Nickster".