Like Tara. If only she'd been a superhero.
And I actually meant that they'd kill her off on How I Met Your Mother so she could appear in this. "And kids, that's the story of how your aunt Robin got hit by a bus and I got her brains splattered all over my new shirt." :p
Edit: The episode will revolve around Ted buying a white shirt and when he visits Lily and Marshall, they'll be like, "there's no way you'll make it through the day without getting a stain on that shirt that you'll never be able to get out." So the whole episode, he'll narrowly avoid getting his shirt dirty, until right at the end when Robin gets hit by a bus and blood splatters on his shirt. And he'll look down at it and make a really annoyed face.
The tag will be Robin's funeral, where Barney will make a hilarious speech about how she was his "bro for life" and "legen... wait for it... dary".