Lately, when he's upset, he says "Ni!" Actually, it's more like, "Mmmmmmmnnni!" It renders what could be exasperating and frustrating (his sleepy-induced crankiness, which is the most difficult crankiness to remedy) into something kind of cute. Yet it remains roughly as fearsome as its more famous counterpart:
Truth be told, though--and I hesitate to write this for fear that it'll jinx it (this is me, knocking wood) (seriously, I just rapped on my desk)--he doesn't fuss much, and lately he falls asleep beautifully at night, if not quite so beautifully in the afternoon. He's quite an agreeable little guy.