Peck Peck Peckin' on Rabbit's Door - S1.E48

When Rabbit settles down for a nap, he finds his rest disturbed by a loud tapping noise. Desperately wanting to sleep, he calls on the Super Sleuths to investigate the annoying sound, which seems to start up every time he lays his head down on the pillow. The Super Sleuths set to work and find themselves on the trail of several mysterious noises. They realize that they need to listen carefully to the noise so as to not simply go chasing after anything that sounds somewhat like it.