After last issue, The Hulk is now mostly mindless and Rick’s to command, right? Well they change the rules on the Hulk again in Incredible Hulk #4 (Sep 1962). After the Hulk is chased across the country and has some fun antics with a movie set, and saves a schoolbus trapped on a railroad, the Hulk returns to the lab with Rick. Rick tries to revert the Hulk back into Bruce Banner and succeeds!
Dr. Banner gets the notion that it might be possible to have the Hulk’s body and his own brain in charge. They perform the experiment, with more doses of gamma rays, and it seems to succeed.
Though it’s noted by Rick that the Hulk seems to have intelligence, but personality-wise seems like a reckless, dangerous brute. Quite different from the mild-mannered military scientist.
I can’t decide if this is just flexing their writing skills or if they actually had a plan for the Hulk, given they have changed the rules of the Hulk metamorphosis in almost as many issues as they’ve had so far.