They say laughter is the best medicine but when a certain clown is involved that is not the case for anyone in Gotham especially Batman.
It’s April fool’s Day and someone is celebrating it in the worst possible way. A garbage barge is floating down the Gotham River. The barge emits a gas that passes over a bridge. A security guard driving an armoured truck starts to smell the gas and begins to laugh, in fact he is laughing so hard he drives the truck into the river.
Bruce Wayne is trying to shave but he is too tired due to his crime fighting antics. He is relieved to hear that Alfred has drawn him a bath. Much to Bruce’s displeasure Alfred shows him a drawing of a bath and says “April Fools”. Bruce has a shower instead. While he is having his shower Bruce hears a news report about near fatal accidents along the riverfront and everyone in that vicinity is acting like total fools. Bruce knows who is causing this mayhem.
Back at the Gotham River we see a submarine floating below the barge. Two men emerge from the sub and break into the newly sunk armoured truck. Inside the sub The Clown Prince of Crime The Joker is listening to a news report about the chaos his gas has caused and we hear the reporter start to breakdown and laugh. The gas has now spread all over Gotham and everyone has lost their minds, they are all just laughing. The Joker and two of his henchmen start stealing everything they can from the citizens of Gotham; they even rob a few stores.
The Batcomputer scans the gas and informs Batman that anyone who has lengthy exposure to the gas will become permanently insane. Batman calls for Alfred but all he hears is Alfred laughing and breaking some of Wayne Manors more expensive trinkets. Batman (wearing a gas mask) sees Alfred going crazy with laughter. He knows he must stop the gas and fast.
Batman finds the barge and uses the Batboat to drag it out to sea so the gas will die down in Gotham and everyone can return to normal. Batman boards the barge and greeted by The Joker, his henchmen and a very tall robotic clown. Batman deals with the henchmen very easily; the robot clown is another matter. The robot releases the barge from the Batboat and it then proceeds to throw Batman into a metal canister and The Joker seals it so Batman can’t get out. The Joker uses a knife to make a few air holes in the canister. Batman somehow manages to avoid being stabbed. The robot throws the canister into the sea and it starts to sink. The air holes have now become water holes. The Joker never knew Batman could sink so low. Inside the canister Batman uses the Batboat remote on his utility belt to get the Batboat laser off a piece of the canister so he can escape and reach the surface.
The Joker is in a junkyard and his men are spraying some laugh toxin on the barge. Batman takes out the henchmen by removing their masks so they feel the full effect of the gas and start to laugh. The robot has a much more grim fate. Batman leads it up to a car crusher and crushes it onto a cube. Batman chases The Joker around the junkyard and he would of got away but he trips on a cable and falls off a ledge (This scene seems familiar somehow). Lucky for The Joker Batman manages to save him, unluckily for The Joker he is going back to Arkham.
Eight showers later Bruce asks how Alfred is. Alfred is distraught that he broke a priceless Ming vase while he was under the gases influence. Bruce tells him not to worry, he will just take the cost of the vase out of Alfred’s salary for the next few years (I guess it isn’t that priceless then). Bruce then gleefully tells Alfred “April Fools”.