The clenched butt cheek walk/run one finds themselves making to reach the nearest toilet before raining a gush of explosive diarrhea in their pants after eating too many chimichangas (or even one funky one).
Got drunk last night and ate 3 chimichangas. Seemed smart at the time, but woke up this morning with the Chimmy Shimmy. Damn near crapped myself!
A Chimmy is a fun-loving person, likes all the good things in life, hanging out and laughing with friends. They are a glass-is-half-full type of person!