In "The Adventures of Buckaroo Banzai Across the Eighth Dimension", Dr Emilio Lizardo gets possessed by Lord John Whorfin when Dr Lizardo used the Oscillation Overthruster to unsuccessfully travel through the Eighth Dimension. How does Whorfin do this? Is this an ability that is unique to him or maybe to the situation (where Dr Lizardo was half stuck in our dimension and half way in the 8th dimension)? If not, then why don't more Red Lectroids do something similar to more humans?
There's no direct answer, but I looked up what I could on Lectroids from Planet 10 (found some info here but it didn't help) and the subtitles from "Pinky Caruthers Unknown Facts" on the The Adventures of Buckaroo Banzai: Special Edition DVD, as well as info from the movie itself.
When Whorfin hears about the overthruster when he's in the institution, he pulls out a device that shocks him and that leads to his memory of the incident where Lizardo broke the dimensional barrier.
When the Black Lectroids need to communicate information to Buckaroo, they do it with an electronic signal. According to the "Unknown Facts" subtitles, the info they passed to Buckaroo in that extremely short burst would have taken an hour to send verbally.
There's no indication, in the movie, book, or from interviews, that Red and Black Lectroids are different species.
The charge from this communication shocks any humans Buckaroo touches for the rest of the movie and even provides some kind of unique charge that brings Penny back to life when she was considered dead.
Lectroids have a way to alter human perception that seems to be organic to their being.
The "Unknown Facts" states that there were times when Lizardo was able to bring his personality out, in spite of Whorfin's best efforts.
Before Lizardo tries to break the dimensional barrier, he kisses and puts on a medallion. (May or may not be important.)
So the Lectroids can send knowledge through electricity to humans in compact form and Whorfin needs an electric shock to regain or relive memories and, apparently, to allow him to take full control of Lizardo's body.
When Lizardo penetrated the dimensional barrier, several Lectroids were in contact with him the full time he was partially in the 8th dimension. Since they can pass information into the human brain electrically, that would be an easy and effective way for Whorfin to "download" his awareness into Lizardo before he was pulled back from the dimensional barrier.
It's also possible that when Lizardo kissed the medallion (leaving some saliva on it), he provided Whorfin a better connection through which to download his consciousness.
I've examined everything I can in Buckaroo canon, and there's never a direct statement about how this is done, so I can't state for sure, but after going through a number of scenes and reading what I could find, it's clear Lectroids use electrical signals and that is most likely how Whorfin's mind was transferred to Lizardo.