The catch? You can never return to our world. State why (or why not) in your post. Note that you'll be leaving all your friends and family behind. Even if you create your own fictional universe, you are limited by your own knowledge of things. So you can simply say "well i create a fictional universe with lasers, plus my friends/family are there" because these new 'friends and family' won't exactly be like the originals. They would simply be fakes, created by your own knowledge of them. E.g., you think your friend likes chocolate, but in reality, he was lying to you. Your 'created friend' will like chocolate, because that is what you believed him to like. This applies to everything about a person; their personality, secrets, etc. So no matter what you do, unless you know literally everything about a person, they will never be the same. This only applies if you are creating your own universe, of course. If you are going into an already created universe, any existing characters would act like their creator imagined.