Set in the 22nd century in the science fiction Star Trek universe, he is the physician aboard the first human Warp 5 capable starship, Enterprise (NX-01), commanded by Captain Jonathan Archer.

He also has great control over his facial muscles, being able to open his mouth wider than humans, as demonstrated by the impossibly large grin he occasionally sports ("Broken Bow", "A Night in Sickbay" and "These Are the Voyages...").

[3] Media website The Digital Fix said that Billingsley delivered a "consistently charming performance", and that he convincingly portrayed Phlox as a doctor, including his ability to transition "from a reassuring bedside manner to one of sombre gravitas".

[5] In 2016, SyFy ranked Phlox #1 of the six main-cast space doctors in the Star Trek franchise,[6] citing his good bedside manner, relaxing demeanor, and success in curing patients, including those partially Borged.

[7] Witney Seibold, writing for Slashfilm, referred to him as Trek's greatest character, describing his sense of humour and Billingsley's accomplished portrayal.

Initially in 2021, he had indicated he had been reluctant to return to the role, partially because of the time needed in makeup playing an alien character with prosthetics.