>This joke is funny because it plays with expectations. The setup of the joke establishes a situation where people from different faiths (a Christian, an atheist, and a Muslim) are coming together and enjoying a drink in harmony, which is unexpected and somewhat surprising. The punchline then takes this unexpected situation and adds another layer of surprise by highlighting the unexpected commonality between the three people (their love of beer).
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>The joke also relies on wordplay, with the phrase "what a cold beer can do" being used in two different ways: first, in the literal sense of what a cold beer can do (quench thirst and refresh), and second, in the figurative sense of what a cold beer can do (bring people together and create harmony).
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>Overall, this joke is funny because it relies on a combination of unexpected twists, wordplay, and the use of common cultural references (such as the idea of people from different faiths enjoying a drink together) to create a humorous effect.