>>121119394 I think it's because she's so genuinely embarrassed by it, reduced to a giggling fit by just admitting it, while Redmayne plays along in a less ashamed way. Anna was a confused teen who didn't understand why they drew Robin so damn sexy with no pants on. Redmayne fell in love with an animal.
It was fun when The Evian Bottle went with a human Flintstones character, to really highlight how out there Redmayne's crush was even if we admit that everyone's had a cartoon one, because there's so many human characters.