Questions on invitation envelopes

I'm printing up my envelopes and I'm wondering how you guys addressed the guest of your invitee. I only know their guest's first name. Should I put:

1) Joe Shmoe & Jenny

or

2) Joe Shmoe & Guest

or

3) go crazy trying to find out this person's last name

I put Joe Shmoe & guest. That way they know they can bring a guest, but it doesn't have to be the guest you listed.

Why dont you call the person and ask for the last name. Or if it is a new boyfreind/girlfreind I think it is ok to put guest. But if they have been together I would try to find out the last name.

Oh ths shame... Etiquette-wise, you're really supposed to write their full names on the invitation if they live together or are married. But, we're not that etiquette obsessed, are we?

I just, in a mad rush, decided to put +guest on a couple of my invites. Woopte doo!

what if I've only met the guest 2x and they don't live together?

we addressed the envelopes of our single friends in their name only, even if they were dating someone (unless it was long-term), but told them that they were more than welcome to bring a date.

ok, I'm just trying to do the right thing over here..

btw now i'm mad! I was going to send my cousin a myspace message asking what her boyfriend's last name was and she deleted me off her myspace! I didn't even notice til now! I knew she was upset that I asked her sister to be in my wedding (who backed out bc she didn't want her sister to be upset) but you don't delete someone off myspace unless it's serious lmao now i'm mad lol lol

These site really helped me navigate through the "etiquette of addressing"

The Knot - Wedding Invitations: Addressing Them

Q: What Are The Correct Titles To Use When Addressing Envelopes? - Wedding Article from WeddingChannel.com