Okay now that we've had a good laugh here's the reason for my post. Sydney and I have identical cups and are always getting them mixed up. I saw this idea on Pinterest and loved it! I don't think the ink will last for a loooong time but it's holding up extremely well. Now Sydney has no reason to use my cup!
Here's a great link to explain it more: http://www.homemadesimple.com/en-ca/crafts/pages/diy-baked-mugs.aspx