Tito had a slight but distinguishable Russian accent which he never managed to get rid of. Speculation has it that the real Tito died during the Spanish Civil War and was replaced by an NKVD agent - the new Tito. These theories were popular in Yugoslavia from 1945 up until the break with Stalin in 1948. Evidence cited pointed to Yugoslav policy which seemed to be dictated from Moscow.

Here's an extract from a CIA report from 1945:

In foreign affairs, as in internal affairs, Russia is the lodestone governing Tito's policies. In every international issue, whether it is the direct concern of Yugoslavia or not, Tito and his press assiduously follow Moscow's lead. In fact, Tito and his followers exhibit a servility toward the Kremlin which contrasts strangely with their otherwise dynamic individuality. It is enough for Moscow to express a view and the Belgrade press reprints it in toto, adding a few biting words of its own. Under these circumstances it is no small wonder that in Belgrade one finds no evidence of a corps of Russian agents directing the activities of individual ministries or agencies. Should the necessity arise for specific guidance, no doubt a brief message from Stalin to Tito would suffice.

Following the break with Stalin in 1948, Tito embarked on a policy of rapprochement with NATO which culminated in discussions about whether to admit Yugoslavia into the organization or not. Milutinovic maintained that Tito was ready to enter the organization but that the Americans were weary of accepting a potential Trojan horse into their back yard.

That said... I have no idea where the truth really stands.

The theory that Tito was in fact not Croatian is also put forward by these insiders. They mention, for example, that nobody in Kumrovac - Tito's alleged place of birth - actually recognised or knew Tito. Other circumstantial evidence is that after WWII, President Tito never met his mother, who was still alive.