In 1972, Christopher auditioned for M*A*S*H* and ended up getting the role of kindhearted Father Francis Mulcahy, though he did not play the role initially.
Christopher also had to learn to box to play the role, as Mulcahy was an amatur boxer.
Once his time as Mulcahy ended, Christopher continued to appear on various television shows, even giving his voice to a few episodes of The Smurfs.
During his audition, Christopher decided to improvise, rather than read the piece given to him.