I actually never really put this in my mind,and I usually watch longer anime series' (like Pokemon etc.)..well I mean I know some short series like AnoHana etc..but it just never really came to mind when I was watching them..so no I haven't.

Well,Hetalia Axis Powers. Other than that,no. But I only finished Hetalia Axis Powers because it's about 5 minutes long.

^ Hmm..How interesting!

^Yeah.

yup. Hetalia (well season 1 at least) and Rosario + Vampire 1 and Capu2 XD

At least I tried! x3

I've seen quite a few anime in one day. If I'm watching a short series then I like to watch it in one go or at least try to watch as much as possible. Some examples of series that I watched all in one go are Baccano!, Omamori Himari and Ichiban Ushiro No Daimaou. In fact I think I watched Omamori Himari and Ichiban both in the same day XD

Hetalia, Elfen Lied, and School Days. Probably because they're short.

I finished Read or Die and Dogs: Bulltes and Carnage in one day, but they're both pretty short.

Only Hanamaru Youchien and that's cause I actually had a day off. T-T
I rarely do.

I watched all of Ika Musume except the last episode in one day. I watched the last one the next day.

NOOOOO.I'm watching animes on TV episode by episode.I haven't tried online sites yet.

Yep, I watched School Days in one day XP

And I've also watched Peach Girl in one day :)

B Gata H Kei :3

I have now, and it was actually Ano Hana too, the picture for this option.

I didn't think it was possible.

Another, AMNESIA, and AIR.

The most resent I remember, but it was only 12 episodes.