Snoopy is lying on top of his doghouse when he hears music. He follows the music and finds a circus unloading. Among other animals, he sees three poodles, and immediately latches onto the white one. He follows her to the entrance of the big top with his tongue hanging out and his pupils shaped like hearts, then stops. Polly, the dog's trainer, sees Snoopy and pulls him inside. The next day, Peppermint Patty calls Charlie Brown to tell him her school gave all students the day off to see the circus. Charlie Brown tells her that his school will be closed as well, and they decide to attend the circus together. At the circus the children see Snoopy perform as part of a dog act. They all realize it is Snoopy and eventually relish his new career, despite Snoopy's shortcomings being completely untrained. However, Charlie Brown isn't having any of it, exclaiming Snoopy's career is being his dog. Later that night, Charlie Brown realizes Snoopy has not returned. He goes to the circus site in time to see Snoopy enter a boxcar, still following Fifi. The gate of the boxcar slams shut on him, and the circus train pulls away. The next scene involves Snoopy trying to find a good warm place to fall asleep while the train is in motion. First he tries to lie on the humps of a camel, only to slide off in between both humps each time, then he finds a lion lying on the ground with its mane spread out on the floor. Snoopy finds this warm enough to settle into and does, but his comfort is short-lived when the lion wakes up and, while it does no harm to Snoopy, he gets scared off, running over the top of a bear, then finds himself in another boxcar filled with props. He decided to lie on top of one box, which turns out to be the saw-a-person-in-half magic trick. He falls into that box and his head and feet appear out the holes in each end. Polly slowly trains Snoopy to become part of the act. First he is given the name Hugo The Great, then he is taught to ride a unicycle first on the ground, then on the high wire. Snoopy also learns to do a back flip and his performance in the next show is an improvement. Meanwhile, back home, Lucy has decided to board up the doorway of Snoopy's doghouse and place a sign on it which reads "Premises Condemned". Charlie Brown also recounts to Linus the story of why his parents gave him a pet dog. Polly decides to expand the act by getting Snoopy and Fifi to do a trapeze act. Snoopy takes to the air a little more fearlessly, Fifi is initially scared. Eventually it works out, and at the next show, combined with the back flips and the unicycle ride, they are a major success. After the show, Polly gives Snoopy and Fifi the good news that they are officially the stars of the circus. However, her boss feels their colors do not fit and wants them both dyed pink. She first wrestles Snoopy into a large vat of food coloring, and after he is completely pink, she goes to do the same to Fifi, but Snoopy jumps between them growling menacingly at her. After Polly shows no fear and tells him basically to get out of her way, Snoopy attacks her and wrestles her into the food coloring until she too is all pink, then jumps out and runs away, taking Fifi with him to the bus stop to return home, but Fifi decides to go back to the circus, then Snoopy sadly boards the bus and returns to Charlie Brown. Back home, Charlie Brown is awakened by the shower running because Snoopy is washing the pink food coloring off him. Charlie Brown sees him exiting the bathroom but says nothing. Snoopy then makes himself some dinner, still crying over being heartbroken from Fifi. Then he realizes that the circus is her life and his home is his life, and he retreats to his doghouse. Upon seeing what Lucy did to it, he rips up the sign and tears the boards off the house. He goes to bed after illuminating a big blinking neon sign which reads "Hugo The Great".
It was one of the first two Peanuts specials released on VHS, on a set release by Media Home Entertainment in June 1984 with You're the Greatest, Charlie Brown. It was also included in the DVD release, Peanuts: Emmy Honored Collection, as well as the DVD release of It's the Easter Beagle, Charlie Brown in the UK from Firefly Entertainment in 2004. It was later included with the deluxe He's Your Dog, Charlie Brown DVD in the US from Warner Home Video on September 21, 2010.