"Boo" is a Season 1 episode of Clifford the Big Red Dog. This episode is the one shown after the episode "Jenna's Sweater". This is also the first and only Halloween themed episode of Clifford the Big Red Dog.
It's Halloween on Birdwell Island, and everybody is dressed up, excited to watch the movie that night. Jenna says nothing scares her and Mac, but when Clifford investigates the big white screen, Clifford gets tangled up in the white sheet, running around like a ghost. Soon, everyone hears spooky noises, and gets scared. Is there really a Ghost Dog of Birdwell Island?
The episode starts with a view of the neighborhood decorated for Halloween. We hear Emily Elizabeth as we soon see Clifford's Dog house. We then see Emily Elizabeth helping Clifford with his costume as she tells him she doesn't want to be late for the Halloween movie. Emily puts some strands of big paper on a paper band around Clifford's head, and says he looks just like a lion. Emily's parents then come out of the house dressed as seashells, and tell Emily and Clifford to hurry so they aren't late for the Halloween movie. Clifford then comes running out of his dog house, dressed as a lion, and both of Emily's parents pretend to act scared, going back into the house. Clifford is concerned, but Emily reassures him her parents are pretending to be scared. Clifford whines, but Emily says it's fun for Halloween. Emily's parents then come out of the house, say Emily and Clifford's costumes look great, and after Emily and Clifford playfully howl, they all head to the beach where the movie will be played.