Bachchan, 75, and Aamir will share the screen space for the first time in the period-action-adventure, slated to hit the screens next Diwali.
The director says he does not fall into the trap of liking or respecting one actor over the other.
"Mr Bachchan is such a senior actor, a big star. Everyone is in awe of him and he is such a great guy to work with. He is totally professional, makes everyone feel at ease.
The director, who has worked with Aamir, 52, in "Dhoom 3", says he does not approach artistes for the sake of it.
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"I never approach an actor till I have finished the script. Once I am done, I discuss it with the actors. In 'Dhoom 3', Aamir and I followed this process because there was a double role, we needed to create two different characters.
Acharya, however, is tight-lipped about the project and hopes the film is shaping well.
"Thugs of Hindostan" also stars Katrina Kaif and Fatima Sana Sheikh.
The director is not new to helming multi-starrers, having debuted with "Tashan", which featured Akshay Kumar, Anil Kapoor, Saif Ali Khan and Kareena Kapoor Khan.
For Acharya, the casting call depends on the script and he considers himself lucky to have got the chance to direct actors who also happen to be stars.
"What I learnt was, a real star never comes on set wearing stardom. Anybody who is at the top of his game will never. Today, the sheer presence of a star cannot make a film work. The film is the star, just that a lot happens between Friday and Monday," he says.
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