Wait so the magic of friendship was beyond twilight for the longest time but she could determine two ponies compatibility as a couple with hardcore mathematics? And as a filly no less?
@Background Pony
[child version of myself]You got a problem with blank flanks?! (stabs him with a dagger)
[normal me] Where did I keep getting the sharp objects as a kid… O_o
Every time Twi and Cadance do that greeting in the show, they’re reminding each other not to tell Shining Armor their secret. Everypony else thought it was a silly in-joke, when it was in fact them celebrating the fact that they “caught” Shining Armor.