What do Stella McCartney, Apple, Netflix, and Wal-Mart have in common? They were all subjects of the most popular episodes of Harvard Business School's Cold Call podcast in the last year.

Twice monthly, host and Chief Marketing and Communications Officer Brian Kenny invites an HBS professor to take listeners behind the scenes of a case he or she has written, probing what inspired the case, exploring how it relates to management practice, and delving into interesting anecdotes that come from researching the case and teaching it in the classroom. The podcast has featured a wide variety of cases covering world-class brands, innovative start-ups, and social enterprises, and the most popular of the more than 30 episodes produced in the past year are listed below.

Though not everyone may know her name, Madam C.J. Walker helped invent what have become staples of our modern country and economy: national sales forces, corporate social responsibility, and, yes, even basic haircare. Orphaned at age 8, married at 14, and widowed at 20 with a daughter to raise, Walker went on to become a millionaire entrepreneur in the Deep South at the turn of the century, against all odds. Professor Nancy Koehn describes Walker’s inspiring real life story of making good on her own unique American dream.

With her unique leadership style and innovative approach to green fashion, Stella McCartney shows that a luxury brand can be sustainable. Professor Anat Keinan discusses her case on the fashion icon.

The European Union recently hit Apple with a $14.5 billion tax bill, but that’s hardly the first or worst financial challenge the technology giant has faced. In 1997, the company suffered a near-death experience that caused it to completely reimagine itself. The result was a new line of products and an unprecedented financial model. Mihir Desai explains the financial wiring behind the inventors of the iPhone.

Running for office requires a lot of public speaking. But often, it’s what candidates aren’t saying that can make or break their campaigns. Take the case of Dan Silver, an experienced congressional candidate that leaves voters cold despite his eminent qualifications. With the help of KNP Communications, Silver is forced to watch himself at the podium and makes some profound discoveries. Professor Amy Cuddy delves into this fascinating case and the importance of body language, believing in your own story, and how to put your best self forward.

It’s been a few months since many of us made New Year’s resolutions. Have you stuck with yours? Professor Leslie John studies how to help people change bad habits (and reinforce good ones) by looking at what makes them tick. Here, she discusses stickK, an application that motivates people by forcing them to put skin in the game of self-improvement.

The TV drama "House of Cards" not only made Netflix a major entertainment player, but it changed the viewing habits of millions of watchers. In this Cold Call Podcast, Anita Elberse discusses her case study on the impact of this pioneering series and the small production company behind it.

Striking a careful balance between professional image and personal passion is difficult, as a case study on high-profile banker and gospel singer Carla Ann Harris underscores. Professor Lakshmi Ramarajan discusses the case in this Cold Call podcast.

Can parents and prospective students trust college rankings? Bill Kirby unpacks this complex system, including what “world-class” actually means, what rankings don’t take into account, and how schools are learning to game an imperfect system.

Since brewing is a marketing-driven business, finding ways to differentiate a beverage from its competition is crucial. Heineken’s chief marketing officer took a novel approach: take the complicated processes of production and distribution and make them interesting and important to the consumer. Professor Forest Reinhardt explains how a big, sophisticated company used small details, from trucking routes to the color of refrigerators, to put its commitment to the environment to work on its behalf.

Can big companies fix big problems? Are they responsible for doing so? As the third-largest employer in the world, any move Wal-mart makes reverberates around the globe. Yet despite its many successes and innovations, particularly in terms of sustainability, the company often faces criticism for its business practices. Professor Rebecca Henderson discusses what she calls the paradigmatic case: how Wal-mart takes huge risks, makes great strides, and demonstrates how companies are one of the few instruments humanity has for changing the world at scale, for better or for worse.