Actually, Crush was 150 years old when Finding Nemo came, so it would make sense that he would be alive in 1900 Manhattan so the only questionable thing about Crush in DS would be being so far up north on the Atlantic (though, ocean currents).
Whoa, I totally forgot about that. Haha. I guess it would be inaccurate as to his surfer dialect and any appearance from other Finding Nemo characters lol.
So I guess just use TSMM as my Ratatouillie justification.