Whenever i hear bad side effects, i think of this from tvtropes. ;)
Side effects of Mxyzptlkacine are uncommon, and include headache, nausea, vomiting, death, dizziness, Vaginal ejaculations, dysentery, cardiac arrhythmia, mild heart explosions, varicose veins, darkened stool, darkened soul, lycanthropy, trucanthropy,…