- Kissing a girl
- Diane also has stealth moves from having a "nosy family"
- Super subtle clue that Diane's done some cheering
Before anyone yells at me, Susan will be appending a "technically" onto this assertion of kssing a girl soon enough, and I am acknowledging here that Justin's gender was still a dude at the time.
I am also asserting that "dude" is a gender (except when it's not).
Panels four and five might well be the ultimate evidence that they're siblings, overshadowing any other evidence imagineable.
My one regret is that I found no way to include complaining about skirts in panel two that didn't feel like throwing off the timing of it.