The interactive videos that I have seen in the last few months have been of a very high standard. Tipp-Ex or shall I say "BIC World Stationary" have released this epic story video that is supper cheesy, but should make you laugh. The ability to get people involved with the brands message or product in a fun way, drives viral behaviour and this campaign is doing exactly that (right now, here). Of course the share buttons are well in your face to share the experience, but I think the action of the viewer is so relevant. It makes you re-type things, like you would when using the product (ok, writing on paper instead). According to Chris Rawlinson, 50 video responses have been made and I recommend you try some of the cool phrases in his post by linking to it here!
Added note: I looked this morning at the YouTube video and less than 24 hours later it now has 1 208 451 views. Massive! On the 7th of September, just 4 days later the video is sitting just shy of 3.5 million views. Considered a viral campaign, great job Tipp-Ex. Also added, I liked the 404 error message if type is unknown and the parental sensory on explicit actions, still entertaining.