Royal watchers are keen to see if Prince Harry, Princess Beatrice and King Willem-Alexander of the Netherlands will be among those taking on the ALS Ice Bucket Challenge.
While the fundraising activity has already seen celebrities including Oprah, Justin Bieber and Gwyneth Paltrow shower themselves with ice cold water, it could now be the turn of some of Europe's royals.
Prince Harry has racked up three nominations for the challenge from singer Ellie Goulding, actress Lindsay Lohan and celebrity chef Jamie Oliver.
Prince Harry has three nominations
"So my manager isn't going to do the ice challenge (but [will] donate)," tweeted Ellie. "So I renominate Prince Harry. Who told me with enough peer pressure..."
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Harry's cousin Princess Beatrice received her nomination from Czech model and former Victoria's Secret Angel Karolina Kurkova, who also tagged Richard Branson, Gayle King and Beatrice's boyfriend Dave Clark.
Princess Beatrice and the Queen have been put up for the challenge
Queen Elizabeth II herself has had two nominations.
"I'd like to nominate the queen of England," declared Gossip Girl star Ed Westwick before having a bucket of ice tipped over his head, while Australian Rules Football player Brad Ebert, whose grandmother suffers from motor neurone disease, also nominated Britain's monarch.
"We're going big here, but hopefully we can get some support," he said on behalf of Port Adelaide Football Club after they had all undertaken the challenge. "We pick the Queen."
Further afield, King Philippe of the Belgians was nominated by Q Music presenter Sven Ornelis. The Belgian monarchy's official Twitter page later posted two pictures of water buckets, naming three new nominees and suggesting that the challenge had been undertaken.
King Willem-Alexander has been nominated while Queen Maxima has supported ALS in the past
King Willem-Alexander of the Netherlands was picked to do the challenge by DJ Martin Garrix, although it is believed that he has declined the invitation.
Royal fans have noted, however, that Willem-Alexander's wife Queen Maxima showed her support for ALS in 2012 when she took part in the Amsterdam City Swim, braving the waters of Amsterdam's canals to raise money for the charity.