My favourite actresses of all time:

(Clockwise) Felicity, Penelope, Natalie, Maggie, Emily, Amy, Tina, Bette, Lisa, Nicole, Judi, Alyson, Vivien, Mary, Kristin, Salma, Julia, Kate, Meryl and SMG
And now I need to tag some people:

(Clockwise) Felicity, Penelope, Natalie, Maggie, Emily, Amy, Tina, Bette, Lisa, Nicole, Judi, Alyson, Vivien, Mary, Kristin, Salma, Julia, Kate, Meryl and SMG
So not only has Alyson Hannigan been gracing us with her presence in CBS's How I Met Your Mother as kindergarten teacher Lily, but she has been doing so with STYLE! (Long gone is the mousy Willow of yore/season1 of HIMYM) Every season Ally finds ways of looking hotter and more stylish and we have to wonder: how much of the costume/makeup/hair budget is allocated to Ally alone? And yet we don't care because we also thank Ally for keeping the Whedonverse in business (Morena Baccarin, Amy Acker, Tom Lenk, and even her beau Alexis Denisof have all been featured in Ally's show).
Thankfully, Hannigan is not only a good Whedon alum when finding co-stars from other Whedon shows; being a good Whedon alum means upholding Whedonesque skills and Ally does this very well. And what is Whedonesque skill #1? Self-awareness.