I had that problems a few months ago with the game Itras By. It's a steamfantasy world in a city rules by a giant spider with all kinds of crazy happening. The introductory adventure in the book strangely is a mystery story about a haunted house. I didn't get in the mood at all because why would my character find that one thing strange?
In D&D it might be easier. There are a few monsters that can be considered quite alien. Flumphs, Modrons, Sahuagin worked for me, when I wanted to have "very strange people to talk to". If that fits your idea of alien, I don't know.
In D&D it might be easier. There are a few monsters that can be considered quite alien. Flumphs, Modrons, Sahuagin worked for me, when I wanted to have "very strange people to talk to". If that fits your idea of alien, I don't know.