AngularJS 1.5.x

var app = angular.module('plunker', []);

app.controller('MainCtrl', function($scope, $http, $q) {
  
  var tvID = '1402-the-walking-dead';
  var tvSeasonDetails = [
    {season_number: 1},
    {season_number: 2},
    {season_number: 3},
    {season_number: 4}];
  
  loadData();
  
  function loadData(){
    var promises = {};

    angular.forEach(tvSeasonDetails, function(tvSeason, key){
        promises[key] = $http.get('https://api.themoviedb.org/3/tv/' + tvID + '/season/' + tvSeason.season_number + '?api_key=7baae7b093159f1876fbe91176adcb32');
    });
  
    $scope.episodeData = [];
    $q.all(promises).then(function(episodesBySeasonNumber){
        angular.forEach(episodesBySeasonNumber, function(response){
            $scope.episodeData.push(response.data);
        });
    });
    
  }
  
});

<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="angular.js@1.5.x" src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.5.10/angular.min.js" data-semver="1.5.10"></script>
    <script src="app.js"></script>
  </head>

  <body ng-controller="MainCtrl">
    <ul>
      <li ng-repeat="season in episodeData">{{season.name}}
          <ul>
              <li ng-repeat="episode in season.episodes">{{episode.name}}</li>
          </ul>
      </li>
  <ul>
  </body>

</html>

/* Put your css in here */