What is up with Rick's (my husband's) WWF game and the user names changing?

Today he saw that on WWF somehow his username, Rick Billionis, got changed to “ZYNGAWF_55578933.” The names of most of the people he’s playing got changed too, but in such a way that they were still recognizable as theirs. For example, our mutual friend, “Cassie Richeter” got changed to Cassassy (which it totally appropriate for her, so that’s weird.)

Others were changed to just the first letter of their first name, then their last name.

What’s REALLY strange is that our mutual friend, Elizabeth Foresman Spots got changed to “Anal Grammar Nazi,” which was her user name on Wis.dm. It made me wonder if there is a hacker who is familiar with Wis.dm.

My name, Valerie Billionis, didn’t change.

All the usernames on his actual facebook pages have stayed the same.

My WWF hasn’t changed.

Any idea what is going on?