I guess running around with a Heterodyne trilobite cutie mark would be a death sentence in Euquestria, so presumably pony-Agatha’s locket would have kept her from developing one, which would be quite embarassing by the time she was a young adult mare.
Probably wouldn’t show up clearly and permanently until the Castle recognized her.
“Gorb. Dis is turning into van of dose plans… Hyu know. De kind vere ve keel everybody dot notices dot vet’s killin’ people?”
“It is?”
“Uh huh. And how do dose always end?”
“De dirigible iz in flames, everybody’z dead an’ I’ve lost my hat.”
“Dot’s right. Und any plan vere you lose you hat iz?”
“A bad plan?”
“Right again!”
Probably wouldn’t show up clearly and permanently until the Castle recognized her.
“It is?”
“Uh huh. And how do dose always end?”
“De dirigible iz in flames, everybody’z dead an’ I’ve lost my hat.”
“Dot’s right. Und any plan vere you lose you hat iz?”
“A bad plan?”
“Right again!”