Depends on how you view reality. If your views are anchored in a perspective that encompasses interdimensional planes, multplie time lines and thus an expanding multiverse then yes it is entirely possible to run into entities that on this what is commonly perceived as the local time space considered fictional.
When leaving this sphere to traverse the inner or outer planes of reality, by this i mean outside the local immediate environment ie (astral, mental, soul planes, infernal empire, arezura, the 9 worlds of norse tradition to name a few) you have left linear time space and entered into planes which may very well have connections into other realities than the local one you left.
At this point the question becomes what practical uses can be gained from this that can result in TANGIBLE PRACTICAL change in your life and the lives of those around you.
Cause unless this occurs it is simply an experience. While experiences can be fun and insightful, unless it results in practical long term results it is pretty much just a mental and energetic exercise.