I'll give you more information here about the reason why this is so funny. By this point in the Book, NASA has literally only just discovered from satellite photography that he is alive on Mars. They have no way of communicating with Mark. Mark for his part has survived 60 Sols. Already a full 30 past the mission standard and it took over a year to get him to Mars. He was left behind on Sol 6. Mark has managed to figure out a method of surviving (he becomes Irish) and has also managed to save himself from being blown up after turning his habitat in to a hydrogen bomb trying to create more water. It's been fairly grim up until now with most of the entries from Mark Watney beginning with "I'm smurfed, I smurfed up and now I'm dead" and NASA are all like "I wonder what being up there alone all this time has done to his psychology?" There is then a cleverly placed page break where the next page contains 2 lines they are:
Quote:
LOG ENTRY: SOL 61
How come Aquaman can control whales? They’re mammals! Makes no sense.
Now in the context of the book that one line entry is without explanation just about the funniest point up until that in the book. I literally laughed my ass off. Making one of the funniest entries in the book something that took place on a 10 day test prior to launch robs the book of one of the best moments of comedy where Mark's overcome many hardships and for just a little while he has a chance, just a chance to relax some instead of wondering what's going to kill him first today.