Renee Zellweger’s Face Is Unrecognizable – What Happened?

You remember Renee Zellweger, right? The Jerry Maguire star used to look like this:

But on Monday night photographers covering a red carpet event for Elle Magazine were scratching their heads wondering who this person was. It was, in fact, Zellweger:

What happened is anyone's guess... Aging? Surgery? Allergic reaction? What do you think?