I am looking for the *closest* number of degrees of separation between
Vin Diesel and Rudolph Valentino within these requirements: 1) the
people who connect these two performers must have been actors, not
directors or producers and 2) the first connection to Vin Diesel and
Valentino must have been an actor/actress who had a role in one of
their films.

Dear shutruknahunte,

This was a most challenging question; it was hard to find any
conncection between Rudolph Valentino and Vin Diesel that meets your
requirements, but I finally found an answer that needs only five
linking persons - which is quite a low number, considering the fact
that Valentino already died in 1926. So here are the degrees of
sparation:

RUDOLPH VALENTINO'S last movie was "The Son of the Sheik" (USA 1926).
In the same movie, Hungarian actress VILMA BÁNKY (1898-1991)
co-starred.

VILMA BÁNKY also starred in the movie "Soll man heiraten?" (Germany
1925). The Russian-German actress OLGA TSCHECHOWA (1897-1980) had a
role in that film.

OLGA TSCHECHOWA appeared in the movie "Burgtheater" (Austria 1936),
together with Austrian actor HANS MOSER (1880-1964).

HANS MOSER played a role in the film "Die schöne Lügnerin" (Austria
1959). This movie also featured the famous French mime and actor
MARCEL MARCEAU (b. 1923).

MARCEL MARCEAU appeared in the TV series "Laugh-In" (USA 1977). So did
American actor ROBIN WILLIAMS (b. 1951).

ROBIN WILLIAMS co-starred in "Awakenings" (USA 1990). This was VIN
DIESEL'S first movie ever - he played the small uncredited role of a
Hospital Orderly.

So this is the connection between Valentino and Diesel: Rudolph
Valentino - Vilma Bánky - Olga Tschechowa - Hans Moser - Marcel
Marceau - Robin Williams - Vin Diesel.

I tried to discover a closer connection with even less linking
persons, but this remained the shortest solution I could find. I hope
it is what you need.

Regards,
Scriptor


Source for the movie casts: Internet Movie Database
http://www.imdb.com/

Hey scriptor, That was pretty amazing research. Bravo, and thank you!

Scriptor is a GENIUS (Official).

Agreed!

I can do it in 3....

Rudolph Valentino was in Character Studies (1921) with Jackie Coogan 
Jackie Coogan was in Escape Artist, The (1982) with M. Emmet Walsh 
M. Emmet Walsh was in Iron Giant, The (1999) with Vin Diesel 


This works if you assume that an animated movie counts as a movie.

You might like to visit the following site, which confirms allegro21's results:
http://www.cs.virginia.edu/oracle/star_links.html