This is a serious question... we're putting in implants to enhance the breasts, but at what point do they look fake? I'm in Texas, many like things big here. "The bigger the better, the tighter the sweater"
There's significant pressure to supersize implants. It's very easy to get caught up in it and I as a plastic surgeon have to fight off every consultation when I'm being asked to place larger implants that I think will look good. Focusing back on your question, the way to make implants not look fake is to maintain a reasonable proportion of breast to implant ratio. If the ratio is much more implant than breast, then it's gonna look like an implant. If the ratio is maintained even, then less so.
Your board certified plastic surgeon will need to help you out on this one. His experience will be key and he will need to understand exactly what you mean by fake so take some photos of patients with similar body frames as yours. If you're overweight, then don't take a photo of an 18 year old, 99 lb playboy model, that's not very helpful. Find a photo of someone similar in characteristics to you and show your doctor a nice and a 'fake' looking result in your opinion. That'll be tremendously helpful.