Why did Alice and Harold laugh when Dave confessed that he'd enlisted a man named Dave?

Alice and Harold found it amusing that Dave had enlisted a man with the same name, creating a humorous situation where they could only picture the confusion that might arise. The absurdity of having a "Dave" serving alongside another "Dave" likely struck them as funny, highlighting the unexpected quirks of life. Additionally, the shared laughter may have strengthened their camaraderie as they bonded over the quirky coincidence.