I saw a template switch to change from having this action on the first post to the last post. But is there a way to get both the first AND last post to popup a preview? If anyone wants to work on this (hopefully wouldn't be too hard), please let me know. This is a pretty standard function and I can't believe no one's thought it up yet.
No. When you mouse over the first post, you get a preview popup. When you'd mouse over the last post, you'd get a completely separate preview bubble, just for the last post. Same as the function on the first post preview.