The holiday cheer in one Canadian city was stifled last week when as many as 15 children received nasty letters signed by their favorite holiday icon: Santa Claus.
Canada Post's annual "Write to Santa" Program encourages kids to send letters to Santa -- addressed to the North Pole, ZIP code 'H0H0H0' -- and for the past 26 years has succeeded in responding to every single child.
Each letter is fairly generic and varies only slightly, just in case more than one letter goes to the same household.
But what's really special about the program is what's at the very end of the letters.
An estimated 11,000 Canada Post volunteers -- current employees and retirees -- add a personal touch to the letters by hand writing a postscript on every one, making sure to reference something specific to the Santa-seeker.
But this year, a not-so-helpful elf seems to have infiltrated the system, adding nasty and obscene postscripts on the reply letters in Ottawa.
"We're committed to not letting this rogue elf impact this beautiful tradition for the children in Ottawa and across Canada who are expecting letters from Santa," said Cindy Daoust, a Canada Post spokeswoman, who said that the volunteers were devastated when they heard the news, many of whom have even offered to take lie-detector tests to exonerate themselves.
The investigation into who is responsible is still ongoing, but Daoust told ABC News that the post office shut down the "Write to Santa" program for two days, and in the process intercepted at least one nasty note that had yet to be delivered. Daoust said that she believes that note will provide a helpful clue in finding the person -- or persons -- responsible for the prank.
The Ottawa Police Department has also joined the investigation.
Mean Letters Crush Boy's Christmas Spirit, Mom Says
"My son must have used 20 pages of paper and wrote [his letter to Santa] in red ink because it had to be perfect," said Ottawa resident Rosalyn Da Costa, whose 11-year-old son, Colton, was one of the 15 who received mean Santa letters. "This blew it right out of the water for him. Now he says 'there really isn't a Santa.'"
Colton's letter had a postscript that read, "Santa is really bad, Santa hates kids and he even hated David Beckham," according to his mother.
Colton had written to Santa requesting a book about the celebrity soccer player.
The rest of the postscript was even worse, and included profanities and sexual references, much like his younger sister's letter did.
Two-and-half-year-old Maya Da Costa's letter, fortunately read by her mother before the tot could see it, read, "This letter is too damn long, you dumb sh--."
Canada Post has since implemented extra security measures for the Santa letters, including requiring each volunteer to sign off on the last names of the children they respond to, making sure every letter's scribe is accounted for.
The postal service also sent two new letters to the Da Costa children in an effort to replace some of the family's missing holiday cheer.
Despite the new letters, Da Costa told ABC News that she's probably not going to participate in the program next year.
"We probably won't write next year, because now I won't trust it anymore," said Da Costa. "I can easily get cute paper and send the letters myself and [my kids] will never know."