User blog comment:Fintin/Caribou new member?/@comment-3242083-20101221015254

It is a difference if you have to kill in order to survive (robin) or celebrate it like caribou (with his retarded praying). He will never join the crew, he is just there to compare the new strong strawhats after the timeskip. Caribou is in the same state the strawhats were 2 years ago, a 210 million supernova.

You can easily notice that - everytime something unexspected happened (kraken, coating problems etc.) caribou completely flips out while the strawhats act unimpressed. They are matured after the 2 years of training - caribou just a rookie.