Suggestions for resistant parents:
-find a time when no one is stressed out to have a conversation. Bad times: after a long work day when everyone is tired, 1 day before a convention and you are still trying to finish up your cosplay. Good time: when you are sitting around shooting the breeze (after a meal? on the front porch? in front of the tv?) Neutral time: in a car (this can be a wonderful time, but there is no escape route if tempers flare, so choose wisely).
-keep calm. Use a low, comfortable, relaxed tone of voice.
-ask the question: why do you dislike my doing cosplay so much? And then *actually listen to their responses* without getting angry. Pause. Take a deep breath. DO NOT RAISE YOUR VOICE. Think of a quiet, rational explanation for why you do it that counteracts their argument. Dad: "You spend too much money on cosplay!" Child: "Dad, I use my own funds to do this. And it keeps me both quietly and happily occupied. Think of the alternatives... I'm not doing drugs. I'm not going out drinking. I'm not sleeping around. Not only that, but I'm learning all sorts of things. I now know all about medieval Scotland having done my research for that Merida costume. Did you know that kilts were originally blankets that were wrapped around the body and not skirts? And that each tartan represents a particular family or clan in Scotland? Plus, I'm getting really good a sewing. Cosplay allows me to explore my creative side. I even get to meet great friends from all over the world."
You get the idea.
-strongly encourage them to come to a Con with you (for ONE day... don't overwhelm them with a huge convention for 4 days!) Try to line up friends to act as ringers for enhancing the experience, i.e. have them introduce themselves politely, make sure they are enthusiastic about cosplay, showcase how clean cut you guys are, etc. Don't spend 6 hours wandering the vendor's hall; take them to some workshops (esp. if they are about making cosplay costumes on the cheap!)
-take them to a masquerade or costume competition show
-randomly offer to mend your dad's pants, socks, pocket, missing buttons, etc so you can showcase your new found sewing abilities.
-try to get your dad (or mom) to watch some anime with you--preferably a complete movie and not a series, at least at first. Talk about the artistic qualities, or read a critical review before you watch. I good choice might be something from Studio Ghibli (you can read Roger Ebert's favorable reviews before starting).
Hope this helps--
Jane <---mom to 3 cosplayers and wife to another