The water dumped on Caesar around 1:27:00 was supposed to be warm, but the crew forgot to heat it up. Caesar's shocked reaction is authentic. They were all apologetic afterward, but Andy Serkis said that it worked for the scene.
Primatologists who saw the film said the apes' behavior was surprisingly realistic. Karin Konoval's performance as Maurice the orangutan was especially noteworthy.
The filmmakers' kids played the young apes in the film. Terry Notary actually trained his kids to "quadruped" and move like apes.
Matt Reeves pointed out that the apes in Rise of the Planet of the Apes (2011) and Dawn of the Planet of the Apes (2014) don't wear clothing. The ape society seen in Planet of the Apes (1968) wears clothing, and Bad Ape is also supposed to be the start of a progression in this direction. To survive in a harsh winter, he wears heavy winter coats he scavenged. This is primarily necessitated by the fact that he is bald, similarly to Rocket. However, while Rocket likely has Alopecia, Bad Ape seems to have lost his hair from old age.
While promoting Dawn of the Planet of the Apes (2014), Andy Serkis was asked if the ALZ-113 drug had also affected apes outside of Caesar's tribe. Matt Reeves and Mark Bomback took note of it, which led to the introduction of "Bad Ape" in this film.