Maureen "Mo" Effanga is a fictional character from the BBC medical drama Holby City, played by actress Chizzy Akudolu. She first appeared in the fourteenth series episode "Double Bubble", broadcast on 22 May 2012. Mo is a consultant cardiothoracic surgeon and a member of Holby's transplant team. She was introduced along with two other regular characters by the show's then executive producer Johnathan Young, who wanted more "truthful and complicated" characters in the series. When Akudolu read the character breakdown for Mo and learned that she was on the transplant team, she knew she wanted the part because she was passionate about organ donation as her brother has had a kidney transplant. The actress met with a heart consultant to help her prepare for the role.

Jonny Maconie is a fictional character from the BBC medical drama Holby City, played by actor Michael Thomson. He first appeared in the fourteenth series episode "Wolf's Clothing", broadcast on 15 May 2012. Jonny is a clinical nurse manager and Holby City Hospital's transplant coordinator. He was introduced along with two other regular cast members by the show's then executive producer Johnathan Young, who wanted more "truthful and complicated" characters in the series. Thomson attended two auditions, before he learned that he had won the part of Jonny. To help him prepare for the role, Thomson went on a tour of a real-life hospital with a heart surgeon. Thomson confirmed his departure from the show in April 2015 and Jonny made his screen exit on 14 April. He returned for a guest appearance on 23 June.