"A Lost Claus" is the Christmas themed special episode of Foster's Home for Imaginary Friends, which premiered December 1, 2005. The episode pays tribute to one of the holiday television chesnuts, A Charlie Brown Christmas as well as Charles Dickens' holiday story A Christmas Carol.
Mac tries to prove that Santa is real.
Mac arrives at Foster's on Christmas Eve to celebrate he and Bloo's first Christmas with the rest of the residents. While Madame Foster is making a popcorn garland, accidentally pricking herself every time, Coco, lays eggs with Christmas decorations inside for the tree, which is done by Wilt. Eduardo comes down the stairway of the busy main hall with his horns painted like candy canes, sleigh bells on his tail and Christmas wreath adorning his skull belt buckle and ties a spring of mistletoe to one of the horns, and kisses Mac and Bloo (who dislikes it) just as Mr. Herriman says that there's bills to be paid wondering where Frankie Foster is this whole time. All of a sudden, Santa Claus arrives. Jolly Old Saint Nick asks Mac and Bloo what they want for Christmas, and just as they are about to tell him their wish lists, a second Santa comes in. Ultimately, after Bloo exchanges larger and larger (and more outrageous gifts), the two Santas get into a fistfight, and Frankie breaks that up, and brings them along with the other Santas of all shapes and sorts to the office of Mr. Herriman, explaining that every year, kids get excited about Santa so they create imaginary ones "that are about as real as my Great Aunt Fanny." Upon hearing that, Mac then has a breakdown disbelieving that there is no such thing as Santa. Bloo, however, is convinced that Mac is wrong, so they go about trying several experiments that would logically prove Santa is real.
Mac doubts that flying reindeer can go around the earth in one night, so Bloo sends Wilt around the world in a sleigh carried by unicorns. He then sets out to disprove the theory that Santa wouldn't fit into the chimney, so he gets Eduardo to slide down. Ed, however, gets stuck. Mac and Bloo then go to the mall to sit on Santa's lap. Santa in the mall turns out to be Coco, and Mac accidentally tears off her fake beard, getting her fired from the job (which she was using to pay for a vacation home) and making her vow never to speak to him again.
When Mac and Bloo get back to the home, Wilt still hasn't returned, so Mac gets even more depressed. Madame Foster, however, informs him that all kids go through this stage sooner or later, but tells him that everything will be all right in the end. Before he goes to sleep, Mac wishes to get underwear from Santa, to try and prove his existence.
Meanwhile, Bloo, who is still disraught over the fact that he is only getting one Christmas present while an imaginary friend named Moishe, a dreidel, tells Bloo he's getting eight gifts (in a reference to Hannukah,) comes up with an idea: scaring the living bejeevers out of Mr. Herriman on Christmas Eve into giving everyone more gifts. In the night, Bloo dresses himself as the ghosts of Bob Marley, a Christmas present, and the robot-ghost of the future, and tells Mr. Herriman to give more than one present to everyone in the house. However, Mr. Herriman misinterprets his message, thinking that it is not to give anyone a single gift. Bloo calls Mac in a state of shock and informs him that there won't be any Christmas in the house, as Mr. Herriman takes out the presents and tree. Christmas morning comes and Mac, along with his mom and his older brother Terrence, are unwrapping presents, as Mac is hoping for what he wished for. He's unhappy until he sees one more gift wrapped up as underwear, but as he opens it, it's a pair of ping-pong ball guns, so Mac asks his mother "What's a guy have to do to get some underwear around here!?" with her answering that maybe she'll give him some on his birthday, then walks off and is next seen heading to Foster's, walking by a decorated dog house and a sorry looking tree akin to A Charlie Brown Christmas and feeling unhappy, but just as he comes through the home's door, Wilt greets him, who having been brought back when, halfway through Africa when all of a sudden, he was suddenly back home. Coco won a wrongful termination suit, filed against the mall operators was settled, and Mac regains her friendship. Eduardo tells Mac that he was pushed down the chimney in the night. And the house is filled with presents and the tree is back in place. Frankie calls the police and describes what happened, believing at last there is a Santa Claus. Madame Foster gives Mac a Christmas stocking with his name on it, and finds out that it's filled with underwear. Mac then realizes that Santa answerd his wish as Madame Foster says "I TOLD you the truth would make itself clear in time." seeing that his faith in Santa's existence is restored. Afterwards, Mac goes to find Bloo to check out one detail. Surely enough, Bloo received a pile of coal (which Mac calls undeniable proof that Santa is real), angrily vows revenge against Santa, saying "Just you wait fat man! ONE DAY I SHALL HAVE MY VENGEANCE!" The house's residents then gather around the tree.
During the end credits, Mr. Herriman panics, trying to tell the ghosts that he tried to take out the presents and pleads to be spared punishment.
Home Video releases