You might have seen his pictures online and squealed over his cuteness.
You might also have spent a good amount of time watching videos of him frolicking about.
But you won't be able to do so anymore.
News of Boo the pomeranian's death broke hearts around the world last Saturday (Jan 19). He was 12.
His death comes after his best friend, fellow pomeranian Buddy, died in 2017.
His owners said on Facebook: "We think his heart literally broke when Buddy left us. He hung on and gave us over a year. But it looks like it was his time, and I'm sure it was a most joyous moment for them when they saw each other in heaven."
Boo's Facebook page following grew steadily over the years to more than 16.5 million after shooting to stardom in 2010.
He has three books to his name: Boo: The Life Of The World's Cutest Dog (2011); Boo: Little Dog In The Big City (2012); and Boo ABC: A To Z With The World's Cutest Dog (2013).
Boo earned US$1 million (S$1.35 million) a year from various sources such as his books and other partnerships, reported HuffPost in 2015.
Other beloved pet pooches have also gained an online following over the years. Here are some other famous dogs on the Internet.
Jiff the pomeranian, also known as Jiffpom, has over 8.9 million followers on Instagram. He appeared in Katy Perry's music video for Dark Horse in 2014, and also has his own emoji line called Jiffmoji.
Pets of the Net, an online calculator created by pet food brand Webbox, suggests that he makes about US$5.6 million a year.
2. Doug the Pug
Another famous dog is Doug the Pug. He has about 3.7 million followers on Instagram, and a net worth of about US$500,000.
Doug is apparently the first verified animal on Spotify and also appeared in an alternative music video for Fall Out Boy's song Irresistible featuring Demi Lovato.
Maru, a shiba inu who lives in Japan, has about 2.5 million followers on Instagram.
His owner Shinjiro Ono began posting more photos of Maru online after the 2011 earthquake and tsunami in Japan, with the hopes of bringing cheer to people after the disaster.
Maru's popularity has since exploded. He has been featured in commercials and photo collections, and has a museum dedicated to him.
In 2015, he was reported by Japanese media to be a tourism ambassador for the Mie prefecture.
The chiweenie - a cross between a chihuahua and a dachshund - is recognisable by his recessed lower jawline and wrinkly neck, and has about two million followers on Instagram.
Tuna was found abandoned on a roadside near San Diego, California, and was taken to a farmers' market in Los Angeles, where he was adopted when he was four months old.
He became famous after being featured online for his cartoonish looks and heartwarming rescue story.
Tuna was also the subject of a meme based on his overbite, which suggested a lisp. In the memes, he was nicknamed Phteven, instead of Steven.
Known for her signature head tilt and tongue that almost always hangs out the side of her mouth, Marnie, a 17-year-old shih tzu, has about two million followers on Instagram.
The permanent slight lean on her head is from a vestibular disease that she had when she was younger.
LA Weekly reported in 2017 that she has since become an ambassador for senior dog adoption. Marnie was adopted by her owner when she was 11.