Even world leaders can take a joke on Twitter, as British Prime Minister David Cameron showed this week when one of his tweets -- and its ensuing parodies -- went viral.

Cameron was all business when he spoke with President Barack Obama by phone to discuss the situation in Ukraine.

“We are united in condemnation of Russia's actions,” he tweeted on Wednesday from his verified Twitter account, adding a photo of him showing concern as he held the phone to his ear.

Within hours, the tweet began to attract thousands of retweets and hilarious, high-profile responses mocking Cameron’s “serious face.”

Comedian Rob Delaney was one of the first to jump on it, making his own serious face while holding a tube of Crest toothpaste to his ear:

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Then beloved Captain Jean-Luc Picard, actor Patrick Stewart, joined in with some Wet Ones, which inspired even more parodies.

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In the end, Cameron gave a glimpse of his own sense of humor with his own reply to Patrick Stewart, posting a photo of another serious conversation, this one a face-to-face with President Bill Clinton.