The "Pigeon" books by Mo Willems. (Baby/Toddler/Preschool/Early Elementary)
Mr. Willems' first "Pigeon" book is now a classic: Don't Let the Pigeon Drive the Bus! There is even a plush toy that says, in Mo Willems' voice, "Let me drive the bus!". Of course, we have that toy pigeon, too.
When I was a children's librarian, I would use at least one of the "Pigeon" books for my story times for the toddlers and pre-schoolers. The toddlers, who had mastered the word "no" loved the book, because they could shout "no" at the book -- something which they probably were discouraged from doing at home. The preschoolers, who still loved to shout "no", understood the humor a bit more and would laugh at the silliness. My favorite memory, however, is when another librarian and I had the pigeon flying a space shuttle for a local kindergarten class. When I, as the pigeon, said "How about I give you five dollars" (to fly the shuttle), one kid piped up, "Make it 20, and we got a deal!" You can't buy that kind of interest in a book.
Now that I have my own young reader, we have the "Smidgeon of Pigeon" books as well as the more sophisticated other "Pigeon" books. My son loves to shout "no" at the books and laugh at the ridiculous pigeon. Again, you can't buy that kind of interest in a "series" of books. You can, however, buy the books, and they are worth every penny.