To be fair, I'd give mad props to Sakurai if he did that one. She only mentions it during the support conversation with her mother, so it's hard to remember.
Minus the part where everyone remembers it.
The thing is, that is one of the very few Support conversations that
everyone saw. When you get a child, they already have a support conversation available with their parents. Lucina is the only one you're guaranteed to get, and that is her C Rank support with her mother, so it's the one unlocked automatically. No matter who you pair, which children you actually acquire, everyone who plays the game is pretty much guaranteed to see her Emmeryn polka-dot dress reference.
And it does rather stick in the mind.
Originally posted in a Robin thread, but it makes more sense here:
I can just see the reveal. Remember the Brand pic of the day?
"You probably won't be able to tell on a TV, but if you zoom in very close, you can see that each of the polka dots is actually Emmeryn's face".
It would immediately get my vote for best pic of the day ever.