I remember being told that it would be the same as participating in the party itself, or holiday if it was christmas cookies, even if you waited until well after. It was compared to people purposely getting disfellowshiped to date an unbeliever.
In third grade a teacher really took pity on me and let me make a construction paper basket with the rest of the class, before easter. I put the basket in my desk so it wouldn't be confused and I wouldn't get easter candy put in when we went to recess. I figured it was JUST a basket if there wasn't any candy. A volunteer parent must have pitied me too, because they took it out of my desk and filled it up. I didn't know what to do. I didn't want to insult people that were just being nice, didn't want things to be wasted, and hoped that if I explained the situation to my mom I would at least get to keep my basket...
I got into the car, mom saw the basket, I told her what happened... she grabbed the basket, marched into the school, SCREAMED at my teacher. So then I was grounded AND in trouble with my teacher.
good times.