Dr. Kubisak was one of the obstetricians in the Season 1 episode Maternity. He was portrayed by actor Ben Parrillo.
Dr. Kubisak meets Dr. Lim in the obstetrics lounge where they find House (who is not supposed to be there as it's for obstetricans only). After reminding House he's not supposed to be there, Kubisak and Lim start telling each other about their sick babies - how they were both fine when they were born but have since gotten sick. House overhears them and comes to the conclusion that they must have both become sick from an epidemic. He quickly leaves the lounge and gets his team together to sweep the maternity ward.
After solving the case, Kubisak and Lim find House in their lounge again. However, this time House has them - he's agreed to deliver the baby of one of his clinic patients, Jill, and even though she's not due for months, that still gives him the right to stay there.