Excerpt from this article:
Egg Gang’s account @world_record_egg first published the egg photo on Jan. 4.
“Let’s set a world record together and get the most liked post on Instagram. Beating the current world record held by Kylie Jenner (18 million)! We got this,” the post says.
By Sunday morning, the egg photo had around 9 million likes; within 10 hours that number had doubled, breaking Jenner’s record. The egg appeared to be getting around a million likes per hour once it started going mega-viral on Sunday.
BuzzFeed News reached out to the mysterious egg account, and the account holder replied that it was actually being run by “Henrietta” — a chicken from the British countryside. Henrietta declined a phone interview but agreed to answer questions via email.
See also this update
UPDATE Feb 6, 2019: And more revealed about the egg, “Instagram’s most-liked egg cracks to reveal a mental health advert” (link to article on BBC).