I have a question...

The other day I went to a restaurant that was a little bit...greasy.
I was with a group of pals from my school and we sat at a table in the back.
When we sat down,
Foster asked if we had seen what was on the lady's plate behind him.
He said it was a chocolate looking sauce that was on all of her food.
My friend Ang and I walked to the restroom and back so we could see the strange sauce.
It was a thick brown sauce that looked disgusting.
When we sat back down we discussed the different possibilities to explain what was on her food.
We could not come up with a concrete explanation so Foster and I asked Ang to ask the waitress what it was.
So she leaned over the table and said "Excuse me can I ask you a question?"
She then said "Do you have any....special sauces?"
She said 'special sauces' in a whisper and the waitress asked "what?"
Ang repeated her question and Foster and I were laughing quite loudly at this point.
The waitress said "I don't know what you are talking about."
So Ang said "What does that lady have on her fries?" while pointing to the lady behind Foster.
The waitress said "Brown gravy."
I don't know what happened next because I had tears in my eyes and stopped paying attention.