Sexual introjects?

So I have this porn star that I used to have sexual fantasies about. Well it got me to wondering...when I'm having a sexual fantasy and it feels real...can it be a sexual introject? Is that even a thing?

Technically, yes, it is possible to have an introject like that. It is possible to have any kind of introject. However, alters split off for a reason--to deal with stress or trauma that no other alter is equipped to do. Sexual alters do exist, but they tend to be because of trauma. It is unlikely that an alter would split off just to please you with no traumatic prompt.