Bob Hoskins portrays the private detective Eddie Valiant, and although the film could be taken as largely a director's film with its flawless use of animation with live action, Hoskins's lead performance is essential to the success of the film. In all of the craziness involving evil judges, a cartoon suspect, and even a looney whole town of cartoons there is Hoskins in the middle. Despite the lunacy going on around him Hoskins never does jump into it himself with his performance instead he acts as hard rock center of sanity within the film as Eddie Valliant whom he portrays like he is playing Jake Gittes in Chinatown. Hoskins importantly takes this role very seriously when lesser actors may not have.
In the role of Eddie Valiant Hoskins plays the private detective as a gruff rather cynical man who is honestly a bit of drunk, and not very happy really about anything. Even though one may, wrongly, say Roger Rabbit is a children's film Hoskins treats the part in a wholly adult fashion. Hoskins does a great job of realizing this over the hill formerly great detective who seems in a bit of a path of nothingness after the death of his brother. Of course I should note that Hoskins does mediate the cynicism properly within Eddie, and he does leave the right amount of life into his character to still make Eddie someone we can easily follow through the film noir murder mystery that Eddie ends up getting involved with.
Hoskins is quite terrific here in that he is able to act as a guide for the audience through world well making Eddie a full fledged character in his own right. One way he does this is through the very important reaction shots through film involving the cartoon characters. On one hand Hoskins does well to ground it all a bit in that he shows properly that Valiant has been around the cartoons for quite some time, and in one way he takes the toons as something that has been there done that. He shows correctly always as Eddie Valiant reacting to the toons in the same way he would to a person the toons are always there because Hoskins certainly never second guesses the fact that they are there.
What works so well about this performance though is that Hoskins just as well interacts with the toons as he should in a more lively way when needed as well such as in Jessica Rabbit's musical number or when he finally ends up in toon town. In say the Jessica Rabbit scene Hoskins is just great in his perfect reactions in his surprise and awe in what Jessica Rabbit ends up being. In the toon town sequence Hoskins almost becomes toon himself yet he still in a odd way manages to stay grounded even when reacting towards the toons on their own terms by playing along with some of their acts such as not falling until realizing he is only standing on air. Hoskins has just the right amount of fun without forgetting the character of Eddie Valiant, and even when absurd he keeps his reactions somehow realistic.
One of the most important aspects of the film is Eddie's relationship with the accused toon Roger Rabbit. Hoskins's performance is especially important here because frankly Roger' antics could wear thin extremely quickly but they do not because of Hoskins being the hard rock of cynicism against him. Their chemistry is excellent because explicitly does not play Eddie for laughs in any obvious fashion as he keeps Eddie always very much in reality. Hoskins though through his more realistic portrayal though actually gets more laughs by finding just the right tone to reign in the craziness in Roger to make the two a rather endearing duo in the end.
Hoskins is terrific in the way though he does honestly establish the cynicism of Eddie as actually coming from his sadness from his brother's death. The few scenes when the sadness is shown directly such as when he is looking over photographs of his brother, or when he retells the story of the death of his brother Hoskins handles them very powerfully creating the appropriate sympathy and understanding for Eddie despite his gruffness. What is especially compelling about Hoskins portrayal here that he even manages to create the transformation within Eddie at the end when he lightens up frankly. It is fat as he never stops to really show this but Hoskins makes work in a delightful fashion by never being too harsh as Eddie earlier, and in just the right deliberate fashion lightening up throughout the film. This is really fantastic performance by Hoskins not only giving an entertaining performance all by himself, but as well making the world of the film come together through his down to earth portrayal in the middle of it all.