I owe you

[Lenka]

I watched a movie (can be said) and there were two girls and wanted to have something to eat. The looked into their fridge and there were small labels on everything (on each piece of food). The labels read "I owe you. Nick". Nick is the name of their friend.
What does it mean? Why did Nick stick the lables on everything? It looked like he wanred them not to eat it, but why would he write "I owe you" on it?

I guess this seems to be just a very simple and funny question to you, doesn't it? Well, I am probably stupid, but I can understand it...

[Tdol]

It means that Nick had eaten their food and left a note to say that he would replace it. They presumably shop separately, but Nick had obviously not done his shopping and had eaten their stuff, but didn't want them to think he was a food thief.