#DogeFather was trending on Twitter on Monday as supporters of Elon Musk, the Tesla CEO and Dogecoin cryptocurrency fan, wished him a happy birthday.

Musk, who was born in Pretoria, South Africa, on June 28, 1971, turned 50 on Tuesday. By 9:30 a.m. ET, approximately 10,700 tweets in the U.S. had been sent using #DogeFather.

Tweets posted by Musk’s fans carrying #DogeFather can be seen below.

The SpaceX CEO is affectionately known as the DogeFather among Dogecoin fans thanks to his relatively long-running association with the digital coin, which was launched in 2013 as a joke based on the Shiba Inu “doge” meme.

In 2019, for instance, Musk tweeted: “Dogecoin might be my fav cryptocurrency. It’s pretty cool.” This came after he won a joke poll on the Dogecoin Twitter account asking who should be its CEO.

His relationship with the coin went mainstream this year amid a cryptocurrency boom. Dogecoin was one of the coins whose value fluctuated following public comments by Musk. His apparent influence on the cryptocurrency market has made him unpopular with some.

In one notable spree in February, Musk, who has 57.5 million Twitter followers, shared tweets including: “Doge,” “Dogecoin is the people’s crypto,” and “No highs, no lows, only Doge.” Shortly after, Dogecoin’s price spiked by 45 percent. This was followed by Dogecoin’s price tanking in May, after Musk called it “a hustle” during a highly anticipated appearance on Saturday Night Live.

On Tuesday, Dogecoin fans also took to the coin’s Reddit page to celebrate the Dogefather’s birthday, with one user sharing a cartoon of the Shiba Inu dog that is the coin’s mascot. It featured the words “many wishes Elon Musk” in the meme’s characteristically stilted language.

Another user shared a photo of Musk with his thumbs up on Monday, above the words: “Whether you love him or hate him…you can’t deny he is forever a part of Dogecoin history. Happy birthday Elon! Thanks for always keeping a sense of humor and you know… creating world changing shit!”

Musk’s milestone birthday was also featured on the “What’s Happening” field on Twitter’s homepage, which highlighted that #HappyBirthdayElonMusk was trending.

Among those to tweeted well-wishes to the billionaire was his mother Maye Musk, who shared a photo of her holding him in her arms as a baby. She wrote: “Thank you for this wonderful day 50 years ago. You have brought me great joy.”

Other high profile figures to wish Musk a happy birthday included former NASA astronaut Garrett Reisman who works with SpaceX.