When Frederick Treves is bring up the oatmeal to John Merrick and Carr Gomm startles him he puts the oatmeal behind his back as to hide it from him. In the next shot he has the oatmeal in front of him and puts it behind his back again while he is walking towards Carr Gomm.
Although it claims to be based on non-fictional writings and primary sources, the movie is full of historical inaccuracies and fictionalized incidents, starting with the fact that Merrick's first name was actually Joseph, not John.
In the film Joseph befriends Dr Treves before he is kidnapped and taken to Belgium. In real life Joseph never met Treves until he was rescued by police from a train station in London as was shown in the film.
00:24:19 Frederick Treves says that Merrick is a complete imbecile probably from birth, then right after that says that he's a complete idiot. Imbecile and idiot were actually psychological terms, the former being someone with an IQ between 26 and 50 and the latter being those with an IQ between 0 and 25, so nobody could be both.