Since Starfleet appears to follow naval protocol and rank hierarchy –
An ensign is an officer; it is the rank bestowed upon graduation from the Naval Academy (although some graduates may be commissioned as a second lieutenant, probably in keeping with their specialty). A sergeant is a non-commissioned officer, i.e., an enlisted man. The closest thing to a sergeant in a navy would probably be a Petty Officer Second Class or above.
And there was, in fact, at least one petty officer IDed by name in Star Trek:TNG – Chief Petty Officer Miles O’Brien, the transporter chief on board the USS Enterprise-D.
Main cast members rejected when Star Trek: TOS was in development
Captain Kirk’s Aunt Hattie, who always warned landing parties to “be careful, now” just before they beamed down and was ready with fresh cookies and milk when they beamed back up.
Lt. Zgrkh Pffftbstwl, curvaceous crew hostess by day, vampire beast by night. And in love with Scotty.
Ensign Maurice Leblanc, responsible for maintaining the quatrotriticale stores and, ironically, a very capable tribble wrangler.
Lt. Nils Lindsstrom, ordained Lutheran minister and chaplain. Originally intended to be a source of comfort and solace upon the loss of comrades, he was cancelled when it was realized that, due to the high mortality rate of redshirts, he would end up with more screen time than Kirk and Spock combined.
CPO Tyrone “Fishbait” Pomeroy, token African-American and ship’s cook; removed when they found Nichelle Nichols and decided on cybercooking.
Dr. Bob “Butcher” Barstowe, who only passed the Federation medical boards exam on the sixth (or was it the seventh?) try and is fleeing Earth ahead of a probably career-ending medical malpractice lawsuit
Ensign Neeb’sh Neidermeyer, young and “by the book” to a fault. Neidermeyer would often interrupt the senior officers’ conversations to interject Star Fleet regulations and to insist on following the Prime Directive to the letter. In a rare for the time instance of continuity and character development, Kirk was going to assign him to the security team and issue him a red shirt midway through the season.
Mr. Fluffy, Ship’s Cat, who would, at least every third episode, be taken over, absorbed or impersonated by an alien - sometimes good, sometimes evil - leading to various zany hijinks
Main cast members rejected when Star Trek: TOS was in development
Captain Kirk’s Aunt Hattie, who always warned landing parties to “be careful, now” just before they beamed down and was ready with fresh cookies and milk when they beamed back up.
Lt. Zgrkh Pffftbstwl, curvaceous crew hostess by day, vampire beast by night. And in love with Scotty.
Ensign Maurice Leblanc, responsible for maintaining the quatrotriticale stores and, ironically, a very capable tribble wrangler.
Lt. Nils Lindsstrom, ordained Lutheran minister and chaplain. Originally intended to be a source of comfort and solace upon the loss of comrades, he was cancelled when it was realized that, due to the high mortality rate of redshirts, he would end up with more screen time than Kirk and Spock combined.
CPO Tyrone “Fishbait” Pomeroy, token African-American and ship’s cook; removed when they found Nichelle Nichols and decided on cybercooking.
Dr. Bob “Butcher” Barstowe, who only passed the Federation medical boards exam on the sixth (or was it the seventh?) try and is fleeing Earth ahead of a probably career-ending medical malpractice lawsuit
Ensign Neeb’sh Neidermeyer, young and “by the book” to a fault. Neidermeyer would often interrupt the senior officers’ conversations to interject Star Fleet regulations and to insist on following the Prime Directive to the letter. In a rare for the time instance of continuity and character development, Kirk was going to assign him to the security team and issue him a red shirt midway through the season.
Mr. Fluffy, Ship’s Cat, who would, at least every third episode, be taken over, absorbed or impersonated by an alien - sometimes good, sometimes evil - leading to various zany hijinks
Lt. Phhhht! - a humanoid alien race whose language is ‘spoken’ via flatulence, and emotions expressed via scent.
Main cast members rejected when Star Trek: TOS was in development
Captain Kirk’s Aunt Hattie, who always warned landing parties to “be careful, now” just before they beamed down and was ready with fresh cookies and milk when they beamed back up.
Lt. Zgrkh Pffftbstwl, curvaceous crew hostess by day, vampire beast by night. And in love with Scotty.
Ensign Maurice Leblanc, responsible for maintaining the quatrotriticale stores and, ironically, a very capable tribble wrangler.
Lt. Nils Lindsstrom, ordained Lutheran minister and chaplain. Originally intended to be a source of comfort and solace upon the loss of comrades, he was cancelled when it was realized that, due to the high mortality rate of redshirts, he would end up with more screen time than Kirk and Spock combined.
CPO Tyrone “Fishbait” Pomeroy, token African-American and ship’s cook; removed when they found Nichelle Nichols and decided on cybercooking.
Dr. Bob “Butcher” Barstowe, who only passed the Federation medical boards exam on the sixth (or was it the seventh?) try and is fleeing Earth ahead of a probably career-ending medical malpractice lawsuit
Ensign Neeb’sh Neidermeyer, young and “by the book” to a fault. Neidermeyer would often interrupt the senior officers’ conversations to interject Star Fleet regulations and to insist on following the Prime Directive to the letter. In a rare for the time instance of continuity and character development, Kirk was going to assign him to the security team and issue him a red shirt midway through the season.
Mr. Fluffy, Ship’s Cat, who would, at least every third episode, be taken over, absorbed or impersonated by an alien - sometimes good, sometimes evil - leading to various zany hijinks
Lt. Phhhht! - a humanoid alien race whose language is ‘spoken’ via flatulence, and emotions expressed via scent.
Cmdr. Spock’s spunky niece T’Ike, who had a knack for getting into trouble but ended every episode with some cute comment that made the senior officers all go, “Awwwww”
An NCO is different from a commissioned officer. Sergeants and petty officers are different from lieutenants and captains with different roles and responsibilities. Officers outrank NCOs and with a few exceptions, service persons do not salute NCOs like an officer would be saluted. But we’re starting to stray here, so…