The Hollywood legend became enamoured with Bradley's pet pooch Charlotte on the set of 'Limitless' and can't resist spoiling the dog when he sees something he thinks she would like.
A source said: "He sent the pooch two pink leather collars and leashes, dog sweaters and treats. Brad was touched."
However, Robert also has a mischievous side and likes playing practical jokes on Bradley whenever he gets the chance.
The source added to National Enquirer magazine: "After finishing 'Limitless', De Niro sent a dozen pizzas to Brad's home with the toppings he hates most – sardines and anchovies."
Robert and Bradley hit it off while working on the movie together and the insider revealed despite the age gap between the 36-year-old Hollywood hunk and the 68-year-old screen veteran, they loved to "get together and eye all the cute actresses and swap war stories about the movies they've made.