YouTube
It shows two adorable British brothers at home. After the younger one, Charlie, takes a bite out of older brother Harry's finger, Harry protests hilariously.
The video has been viewed more than 800 million times since it was uploaded eight years ago.
Charlie and Harry are an internet sensation now, but it turns out the video was never even meant to be seen by the public.
According to an interview with CBBC this week, the boys' father originally uploaded the video to YouTube only because the file was too big to send to friends and family over email.
It went on to become the biggest viral hit in YouTube history, not taking music videos into account. According to CBBC, the video has gotten more views than videos posted by pop stars like Taylor Swift, One Direction, and Adele.
Eight years later, the family has earned thousands of dollars in advertising and sponsorship deals. The boys are now 8 and 11 years old.
"We've always viewed the YouTube thing as a hobby," their father, Howard, said to CBBC. "It brings in a bit of extra money so we can be more comfortable."
See their full interview with CBBC.