There has been a question that has perplexed Trekkies for decades: just what is going on with Chief O'Brien's rank?
The franchise's favorite hard working everyman started out as just a glorified extra for the first season of the The Next Generation, filling in on the bridge whenever Geordi or Worf was away. It would not be until the second episode of Season 2 that he got a name then it wouldn't be till the second episode of Season 4 that we learn he was actually enlisted and not an officer. In the fourth season of Deep Space Nine his rank settles at Chief Petty Officer (complete newly designed rank insignia).
However if we add the comic book continuity to this things go really strange...
O'Brien not long after coming aboard the Enterprise-D, rank of Ensign. For the love of... what had you done O'Brien to be demoted four steps in rank?
Episode 20 of Season Two, O'Brien has been doing good for him self, he got bumped back up to Lieutenant back in Episode 1 of this season...
... only to be busted to Lieutenant Junior Grade by the end of the episode.
Nope. back up to full Lieutenant just in time for Worf's adoptive father to declare him a Chief. Worf's father says it then it must be so: turn in your pips.
By Season 6 of TNG O'Brien gets the single hollow pip of Chief. This is the look of a man who realizes he must now take orders from Lieutenant Barclay.
Reassigned to a ramshackle space station called Deep Space Nine, O'Brien manages to hold on to his single half pip for four seasons until he is graced with a promotion to Lieutenant Junior Grade bringing him back to the realm of officers... at least for the length of the issue:
By the fourth episode of Season 4, Starfleet decides to just make a rank especially for O'Brien (we only see one other person with this rank insignia in the entire franchise and for her it is a temporary rank), they must have realized that further demotions are unnecessary as simply being Miles Edward O'Brien is punishment enough.
Closing Thought: Colm Meanely who plays the Chief is second to only Michael Dorn in the number of Star Trek appearances, showing up in 211 episodes and in both the pilot and finale of two series, not bad for someone who started as just a day player on the show.