Who is Smolka, Mandel and Bubbles from Portnoy's Complaint and what is their importance?

These three individuals were, according to Alex, present at the occasion of his first sexual experience—Smolka and Mandel were his friends, Bubbles was the grudgingly available teenage girl with whom Alex had that experience. Alex portrays Smolka and Mandel as being "bad boys", and is later surprised to learn that they have both become very successful businessmen and husbands.