Isn't that weird when that happens?  I had someone buy a Halloween card at Valentine's Day.  Best I can figure they are those folks who buy cards they like when they see them and can actually find them when the holidays come around again...unlike me who finds a stash of them years later when I wasn't looking for them! 

Weird but great!  We see a lot of these add on sales.  It certainly means the shopper has come for one specific card and while they're here have found other cards that they like.