Due how fast the credits flip from page to page, character animations are absent, except for the ball and Blue before the book closes.
Steve knocks on the screen at the beginning of this episode.
This is the only time Steve physically interacts with the fourth wall by knocking.
The sound effect used for knocking on the screen resembles that of an older glass TV screen. Nowadays, more TV's used plastic instead of glass for screens, so this break in the fourth wall is a little dated.
Steve checking out the book Another Really Great Book is a reference to the book A Really Great Book from Blue's ABCs.
Blue licks at the viewer on the screen. The first episode that happened was on Blue's Birthday.
This is the eighth time Steve wears his tan shoes.