Busybody who always needs to ask where one's lunch has come from, even if it's obvious. Every ingredient must be accounted for.
Zeke: How come you didn't have lunch with us today, Clyde?
Clyde: I got caught by the phantom gourmet. Of course she had to ask me if I'd gotten my burger at Wendy's. I said, "What gave it away? The bag that says 'Wendy's' on it?"
While on a dinner date, secretly jerk off into your hand. Wait until the girl gets up to use the bathroom, or distract her in some way. When she's not looking BAM! into her salad/food. Works particularly well if she's having fettuccine alfredo or some similar dish.
I was out to dinner with my girl last night. She got fettuccine alfredo, so when she wasn't looking I pulled a phantom gourmet and threw a fist full of cum in her food. She never figured out why the alfredo sauce was so salty.