If you get invited over to someones house for dinner, except their invitation, but eat before going over to their house. My dad said that its rude to do that, since my cousin did something like that on a family vacation. We were going to a nice restaurant for dinner one night. So, my cousin and my brother walk over to a close by sonic just to get a slushie, due to the long wait. My cousin also buys a hamburger, right before a nice dinner. I thought it was stupid, but not really rude.