To suddenly, and with seemingly no cause, spill one's shit all over the place. Those who "Pull Kelly's" are often repeat offenders, and cannot be trusted to carry or otherwise posses plates of food, bowls of soup, glasses, mugs, any other similar containers, or basically anything that would be really inconvenient to clean.
WOW! Way to Pull a Kelly and spill pasta and kool aid all over the nice white carpet!