Other communicators appearing through different mediums often include a range of deceased celebrities: Freddy Mercury, Louis Armstrong etc...
In the realm of musical mediumship it is not unkown for composers to channel new music through more than one medium: Liszt and Chopin appear to be common channeling composers.
Grubelei transmitted by Franz Liszt through the mediumship of Rosemary Brown (1916-2001).
In his book Pursuing Physical Mediumship (2007), Robin Foy details various communicators that have not limited their contact with this plane through just one medium. Foy recounts numerous situations in which communications have been received through different mediums (including Leslie Flint) from the likes of Winston Churchill, Oscar Wilde, Emily Bronte, Sir Oliver Lodge, Sir William Crookes, Sir Arthur Conan Doyle and so on.
Winston Churchill communicating through the mediumship of Leslie Flint (1911-1994) in 1980.
Indeed, there appears to be a propensity towards receiving communications from those individuals who were at one time themselves engaged in the investigation of spiritualistic phenomena. This is, perhaps, as we would expect: an individual that had been fascinated with the mechanics of mediumship throughout life would not hesitate to explore that machinery first-hand when given the opportunity in the afterlife.
Interestingly we also find accounts of communications with those who were skeptical in life, who now, upon experiencing the truth of life after death for themselves, cannot resist but come to communicate how misguided they had been in life. This situation, naturally, seems suspect to any inquisitive researcher (the medium might well be faking it in order to "demonstrate" the truth of life after death and to prove that his/her critics were ultimately wrong) , but it cannot be denied that it is a distinct possibility; we shouldn't rule it out just because it appears improbable, but we'd ought to remain inquisitive.
One argument put forward to account for the recurrence of "celebrity communicators" is that certain discarnate entities will utilise a famous name in order to enhance the enthusiasm of the sitters to communicate, thusly resulting in far stronger phenomena.
Celebrity "possession cults" are not limited to this particular form. The Changun possession cult of Korea is solely centred around the incorporation of famous deceased generals, including the likes of Genghis Khan during the Kut ceremony:
I would suggest, perhaps, that if these entities are not in actuality the individuals they claim to be, that the utilisation of the name of a celebrity/general is to denote elevation. The human being might find that attributing the label of a well known and respected individual to an unknown spiritual entity enables them to better conceive of the "elevatedness" of the entity. By giving it the name of a general, for instance, it is implied that the being is above our status. Conceiving of the spirit as "above our status" might simply be a means for us to abstractify higher dimensionality; I am "normal", the communicator is not; a way of communicating the sense of an uncanny presence.
Some food for thought perhaps...