Otis is using understandable sentences that have moved up both in clarity and complexity. For quite some time he has been saying things that are formally sentences but which to get his actual meaning, you would have to add a word or two, e.g. “Otis, do it.” really means “Otis will do it.” Although, the related “Papa, do it” is clear enough.
He is also relating to the cats more directly. Talking to them, etc.: “Look Molly, flower.” After he picked a daffodil in the yard and was carrying it around.
A big question of Otis’s these days is: “What’s that noise!” Usually followed by “Find out!” when he runs off to determine the source of the sound. Popular noises include: the furnace, the cat’s drinking fountain, the refrigerator, and such. Sometimes his new awareness of sounds leaves him nervous, but I encourage him to figure out the source and be “the master of noises.”
He still likes the music, and his current favorite song is Etta James’s version of Groove Me.