The pictures, starring Stiller and Robert De Niro, grossed more than $846 million worldwide and the third installment, Little Fockers, is set to hit screens later this month (Dec10).
And Stiller has now revealed he's penned a fourth script and hopes to convince funnyman Will Ferrell to appear in the next comedy.
He tells Britain's Daily Record, "Will (Ferrell)? Hopefully. We finished the script and hopefully we'll shoot it next year."