Things that gave the animorphs away

[yunyun]

Like the title says, things that gave the animorphs away. And again I don't know if this has been started before but I don't go to page 10 looking for something like this.
 I personally think that when Rachel called this yeerk in 45 "mr" that was sorta...un-andalite-ish in my opinion.
 Anything else to add?

[TobiasMasonPark]

     Marco and the Ten Commandments reference.

[Dogman15]

It was specifically a reference to The Prince of Egypt, a December 18, 1998 DreamWorks Animation film. By the standards of book 30, this is a very recent pop culture reference for Marco. The Reunion was published in June 1999, but by my own calculations at http://en.wikipedia.org/wiki/Chronological_list_of_Animorphs_books, it takes place in 1998. My theory is that Marco knew of the upcoming film by way of publicity and advertising, but since it hadn't come out yet, he hadn't seen it. Knowing about it was enough to be able to make a reference to it. He said "Not to get all Prince of Egypt on you, but... Behold!" (when "revealing" the Hork-Bajir valley.)

In addition to that, Visser One also discovered that the rest of them were humans when they have her hostage towards the end of Visser. Marco calls Cassie (Polar Bear) by name, and Jake (Tiger) speaks in a non-Andalite way.

[TobiasMasonPark]

     The pants they found during the message.

[Chad32]

In 7 the Anis demorph after getting eaten by a Taxxon in roach morph. There's no way the controllers would mistake Humans covered in entrails as Andalites, and Rachel is even surprised that a Human controller would strike a girl when he attacked. That means she admits that he should have been able to recognize her as a Human female.