Sandra Boynton's books seem to have a natural cadence for toddlers to put in their own sub-comments inbetween turning pages.

Stacia's copy of "Oh My, Oh My, Oh Dinosaurs!" has a commentary stream that goes:

Dinosaurs Happy - "Happy Birthday!"
Dinosaurs Sad - "They broke the balloon!"
Dinosaurs Good - "Painting!"
Dinosaurs Bad - "Messy!"
Dinosaurs Weak - "Can't reach it!"
Dinosaurs Strong - "Pick up whole tree"
"Dinosaurs Singing a Dinosaur Song!" (in quite good tune!)
Dinosaurs Cute - "Daddy and Stacia!"
Dinosaurs Not - "Mommy!"
Etc..

These books are boundlessly read at bedtime, and "Pajama Time!" has been a god-send for making bedtime happen! "Birthday Monsters" is just plain wierd!