Due to a coding flaw, Beast the dog is the only member of the Zuckerberg household who can be blocked on Facebook.
Company founder Mark Zuckerberg and his wife Priscilla have already been blocked too many times for any more blocking by Facebook's two billion users to be effective.
Beast, who is a puli, a type of Hungarian sheepdog, has his own Facebook profile and can be blocked by anyone cruel enough to try. The dog, described by Facebook as a public figure, rose to fame after appearing like an enormous kitchen mop in a Zuckerberg family photo.
Despite claims from Facebook users that not being able to block the Zuckerbergs is unfair, the social network has an explanation.
Because of how the blocking system has been coded, there is a finite number of blocks each profile can be subjected to. After that, the system no longer works properly and throws up an error for any new blocking attempt.
Blocking the Zuckerbergs is a two-step process. First, clicking block brings up the same warning as blocking anyone else. "Are you sure?," Facebook asks, before outlining how Mark and Priscilla will now longer see your posts, talk to you, or add you as a friend. All of which seem fairly unlikely anyway.
But, where clicking confirm should be the end of it, a second message appears. "This profile can't be blocked for now," it reads. "You can report Pages or profiles if you think they're doing something that goes against our Community Standards...If you think you're seeing this by mistake, please let us know."
Acknowledging this earlier in 2017, Facebook told the Guardian: "This error isn't specific to any one account. It's generated when a person has been blocked a certain large number of times. In very rare instances, a viral campaign will develop instructing lots of people to all wrongly block the same person."
Blocking Beast, if you must, returns the message: "You've blocked Beast. We're sorry that you've had this experience." Thankfully, you can unblock him just as easily.