Dreams involving aliens often symbolize feelings of fear or the unknown. The alien in your garage could represent something in your life that feels foreign or unsettling. It might be an issue or emotion you are grappling with that you find difficult to confront.

Your action of slamming the door shut suggests a desire to protect yourself from this unsettling feeling or situation. Seeking your father's help indicates that you may be looking for support or guidance in dealing with this issue. However, your father's reaction—closing the door back up—might reflect feelings of helplessness or inadequacy in dealing with challenges together.

This dream could be encouraging you to face the unknown or uncomfortable aspects of your life rather than avoiding them. Consider what areas in your waking life feel alien or overwhelming and explore ways to address them. It might be beneficial to reach out to a trusted friend or family member for support, as your father represents a source of guidance in your dream.