Fatty, the Snortlepig, The Dude or just dude (my dad always refers to her as the dude or 'dudey' now, it's cute; my sister invariably greets her with "Yo, dudely one!"), Tiny, Tiny Tard (DH's)
, You Tiny Thing, fishie, squishy one, little Gordita, Gordita-creeter, Sir Stink-a-lot, Tiny Pesk, Fatcheeks, the HMS Crazybaby, Shuttlepod 1, chicken-child, Dribbly Pig...
Now I look at the list, they all seem a tad derogatory.
Poor kid. And DH and I are always interrupting her baby gurgles to say "Little dude, your opinion is very tiny". Meh, at least if she grows up broke in the head we'll know why.