OH MY GOD IT WAS SANTA ALL ALONG! I WAS RIGHT AFTER ALL!
You all thought I was crazy, but I was on the ball! Unlike the rest of you, who fell off your balls! It was difficult with all you naysayers trying to knock me down, but I stayed on that ball! Uphill, downhill, through rain and ice, I never fell! Now you're all on the ground, wondering where your balls have gone off to, and I'm still on mine!
In. Your. FACE!
Okay, in all seriousness, odds are good that this isn't really Santa Claus. I think I've got a ways to go before I go that far off the deep end, but I'm getting there. I'll keep trying, doing my best, and maybe, just maybe, one day I will successfully go completely off my rocker and jump over dozens of sharks.
Anyway, the rest of the comic. Grace, I hate to say it, but... Worst. Super hero. EVER. What kind of super hero trips over a dropped water bottle? Don't they have sixth senses for that sort of thing? Anyway, there needed to be some reason for Grace to fall behind, and it was originally just going to be that Susan took off running unexpectedly, but Grace could easily catch up with Susan. She needed a handicap, and having it technically be Sarah's fault seemed like a slight bit of mercy for Grace's ego.
One question I've gotten is in regard to questions lacking question marks and statements with question marks. This is intended to indicate a tone. When a question is generally asked, the tone changes at the end to signify a question. The idea of having the question mark there when it isn't a question is to imply that sort of tone in spite of it not being a question (think the "Valley Girl" stereotype), whereas the lack of a question mark on a question generally suggests the question doesn't have that tone shift, possibly being flat, curt, and/or simply sounding like a statement.