The term 'You May Get Fooled When It Arrives' is referring to the month of APRIL, which has five letters. APRIL is known as a month of pranks and jokes, as it is the month when APRIL Fool's Day is celebrated. This day is a day of practical jokes and hoaxes, and people are often tricked into believing something that is not true. As such, the term 'You May Get Fooled When It Arrives' is a warning to be wary of APRIL and the tricks that may come with it.