Heffernan returned to Australia and began working for World Championship Wrestling (the Australian version, not the North American wrestling federation) under booker Jim Barnett as a singles wrestler. Costello was originally supposed to return to Australia as well and work for WCW, but those plans never came through. Instead, Costello remained in the United States and kept working in the tag team division, never seeking a career as a singles wrestler. Costello began wrestling for Georgia Championship Wrestling, where he teamed up with Louis Tillet to form a tag team known as "The Globetrotters"; a name that played off Costello's Australian and Tillet's French heritage. The Globetrotters defeated the Mysterious Medics in the finals of the Georgia NWA World Tag Team Championship but only held the titles for a week before losing them to Kurt and Karl Von Brauner on 4 February 1966. After this, the Globetrotters broke up due to differences in their approach to tag teaming.  Costello then moved to the NWA Mid-America territory near Nashville, Tennessee. In Mid-American, Costello teamed with Herb Welch to win the Mid-American version of the NWA World Tag Team Championship, which they held for just over 2 months. While still working in Mid-America, Costello began to team with Karl Von Brauner, who used a "German Nazi" gimmick despite being American. Under the management of "Playboy" Gary Hart, Costello and Von Brauner were billed as "The Internationals"; the team was later managed by George "Crybaby" Cannon. The Internationals worked mainly in Tennessee and Texas for NWA Western States. In Texas, Costello and Von Brauner won the Texas version of the NWA World Tag Team Championship, a title Costello and Heffernan had held in 1958. The team was also billed as the first NWA American Tag Team Champions, titles that were also recognized by World Class Championship Wrestling in addition to the Western States promotion. The Internationals lost the American Tag Team title to Fritz and Waldo Von Erich on 21 February 1967. Kurt then decided to go back to teaming with his storyline brother, Karl Von Brauner.  After the Internationals broke up, Costello returned to Australia to visit friends and relatives and to recuperate after many years on the road. On his way back to the United States, Costello had a stop over in Detroit, Michigan, where he met Cleo Williams. The two fell in love and married shortly afterwards, remaining together for the rest of Costello's life.

Answer this question "What did Costello do while he was away from the Kangaroos?" by extracting the answer from the text above.
Heffernan returned to Australia and began working for World Championship Wrestling (the Australian version, not the North American wrestling federation) under booker Jim Barnett as a singles wrestler.