April Fish has the same connotations as April Fools, not only in being the first day of April, but deemed as a day of foolishness. A French tradition that I will not purport to understand its origin; although I have read a few explanations of its beginning, there are differing stories and no concrete evidence pointing to any one story's validity. Let's just take it for what it is, a day to not take life too seriously and have a little fun for the day.
However, remember this . . . if you're the only one left laughing, your joke probably wasn't very funny in the first place. Humor works best when it's at everybody's expense and within everyone's experience.
Happy April Fish!!!