Will is pretty interested in trains (choo-choos, sounds like "doodoo"). He has been for a long time now - ever since he got his first choo-choo book (still one of his favorites which we bring out for long car trips). He has a few choo-choo toys, and any group of non-train toys can become a choo-choo by placing them in a row. Also, when he rides on my shoulders, we call it riding the "dad train" - similarly, Will likes to ride grandpa and uncle trains - and when Will yells "choo-choo!" and pumps his arms the dad train goes fast.
Anyway, these choo-choo bath toys have become some of his favorites, to the point that he has named them. The blue one's name is "dada", the green one's name is "dukie", and the red one's name is... "dada". That's right, there are two dadas. He consistently refers to them this way. For the record, this choo-choo is named "mama" - in the video, when I ask him which one is mama, he's confused because the mama train lives in the downstairs toybasket, not with the bathroom toys.