Walk-ins are where there is more than one soul in a single physical body. You could be the walk-in, or you could have one with you.

There are 5 main types of walk-ins that all have very distinct traits. They also have different effects on the body or on someone’s mental health.
<...>
Walk-in #1: Human Bound / Braided Soul / Twin Flame
These beings have created some form of soul bond. It is two human souls in a physical vessel, often accompanied by overarching themes of love stories, savior stories, or themes of dependence.
<...>
This type of walk-in brings some of the most physical issues and even mental diagnoses. From doing over 4,000 client sessions, I have seen a lot of people diagnosed with things such as: bipolar, BPD, multiple personality disorder that have some form of walk-in amplifying the patterns in which they experience symptoms.
<...>
Walk-in #2: Lower Vibrational Energetic Match Walk-In’s
Common to near death experiences, substance use or other forms of loss of consciousness is the energetic match walk-in.

This is an example of times where someone can step into a body who is not an enlightened soul.
<...>
Walk-in #3: The Original Occupant
With the original occupant, we often see another person or being who has gone further in their spiritual development work being “hired” to a family line to lighten the load.
<...>
Walk-in #4: The Starseed Walk-In
Starseed Walk-Ins are here to raise the consciousness of humanity. We are here to integrate our wisdom from other planets, incarnations and galaxies.
<...>
Walk- in #5: Galactic level walk-in

These advanced beings have no ancestral karma or family baggage, they are simply here to be activators and experiencers. They do not have to lead with their trauma and do not have to go through the emotional depths of dark night of the souls. Instead, they step into leader and visionary roles naturally.

Famous galactic level walk-in’s range from Elon Musk to Nicolas Tesla.