Probably something suspicious.

Barris Offee, Jedi Padawan awoke with a start, this start was most likely instigated by the bright blue water balloon impacting her face at a high velocity and quite effectively removing her from her sleep. She shot out of her bed only to find her attacker was nowhere to be seen and a really rather large bucket of water balloons all in her favourite colour of a nice deep forest green were siting by the door with a note attached to said bucket reading 'Arm yourself'. All across the Jedi Temple people were waking to a similar situation causing them to rush out of their rooms to attempt to hunt their attackers down, the only unfortunate miscalculation was that nobody seemed to have that particular shade of blue as their water balloon. In the typical slow and methodical Jedi fashion the calm investigation of who provided the water balloons was interrupted by Jedi Knight Anakin Skywalker, who had instead woken up to a bright pink water ballon to the face slightly after everyone else throwing investigation to the wind by very maturely and in true Jedi fashion throwing a water balloon (in black) at the first person he saw, unfortunately this person was Jedi Master Yoda, the Grandmaster of the Jedi Order who was levitating a bucket of Neon Yellow water balloons behind him as he walked along the corridor and promptly soaking the short green being. This, future Jedi scholars would refer to as the catalyst for the creation of the Annual Jedi-Order-Water-Balloon-Battle

The moment the balloon exploded on Master Yoda's face chaos broke out, the spell of calm investigation surrounding the Jedi Order was broken and the immediate response was for the water balloons to be thrown everywhere and at everyone with wild abandon, utilising every available tool, be it they're hands, the Force, or in a one particularly inventive Jedi's case, a two meter wide catapult quickly improvised from a nearby wall section and some chewing gum. Jedi Padawan Ahsoka Tano quickly learnt the hard way that cutting a water balloon in half with a quick swipe of her backhanded Lightsaber was in fact, a bad idea. The battle would rate on for hours with nobody stopping to wonder as to why they hadn't run out of water balloons and why this all happened in the first place. By the end of that day approximately nothing productive had been done and the temple cleaning droids were not looking very exited at the prospect of having to fix the mess made by the warring Jedi. The catapult had succumbed to Master Plo Koon's Lightsaber after being a bit too inclined towards hitting him. Master Skywalker was laying unconscious in a fountain after attempting foolishly to use the force to direct the water flow towards his enemies. And Master Yoda was dripping a lot while looking sadly at his hoverchair as it sparked rather sadly after being taken down by multiple simultaneous water balloons when he attempted to gain air superiority.

Nobody noticed Master Mace Windu sitting on one of the chairs in the Jedi Temple security room with a suspiciously victorious smirk on his face and his satisfaction rippling through the force, 'and they say I have no sense of humor' He thought rather smugly.