They know I have a can collection but we've never really talked about it much. So when I asked for this one he was surprised I didn't already have such a common, current can. But I told him I don't drink soda and I can't just buy sodas to empty them out for the cans. So I just ask for people's trash.
He was surprised with some of my stats (such as I started collecting in 2011, have over 6000 cans now, have cans from many countries, etc.).
He also recommended when the day comes that I show all the boxes of cans to my kids and reveal they'll all be theirs someday, not to be upset if they ask, "So, how much do you think all these weigh?"