Long before he came on screen as Dolittle there was his time as one of Marvel's favorite super heroes. He proved on screen that he could be take on the role of a mentor with Peter Parker that is played by Tom Holland. It seems that Robert Downey Jr is just like the on set dad for the younger actors.
As he did the same thing with his Dolittle costar, Harry Collett. Harry Collett plays the role of Tommy Stubbins. The man who helps Dolittle through the movie.