A C182 ACFT TAKES THE RWY AFTER TWR CTLR CLRED HIM INTO POS AND HOLD. CTLR THEN USED ANOTHER CALL SIGN FOR TKOF CLRNC WHICH CREATED A POTENTIAL GND CONFLICT IN DELAYING THE TKOF AT APA; CO.

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THE PROB AROSE MOST LIKELY FROM A SUDDEN INCREASE IN THE NUMBER OF AIRPLANES CONTACTING CENTENNIAL TWR AND NEEDING TO TAKE OFF; LAND; OR JOIN THE TFC PATTERN. THE TWR CTLR'S VOICE WAS CLRLY STRESSED AND SHE SOUNDED FLUSTERED. I THINK SHE LOST TRACK OF WHO WAS WHO; AND THAT FLUSTERED HER EVEN MORE. IT DIDN'T HELP THAT THERE WAS A PLT IN THE PATTERN WHO CUT SOMEBODY OFF AND WAS NOT FOLLOWING INSTRUCTIONS. HERE'S WHAT HAPPENED: AFTER WE FINISHED OUR RUN-UP; WE CONTACTED CENTENNIAL GND (NORMAL PROC THERE) TO SAY WE WERE READY FOR DEP FROM RWY 17L AND WERE GOING TO STAY IN THE PATTERN FOR TOUCH-AND-GOES (RWY 17R WAS BEING USED FOR TOUCH-AND-GO TFC). THE GND CTLR TOLD US TO 'HOLD SHORT AND MONITOR TWR (ON 118.90).' WE TAXIED TO THE HOLD SHORT LINE OF RWY 17L AND STOPPED WITH THE PLANE SLIGHTLY FACING A DIRECTION FROM WHICH WE COULD SEE FINAL FOR RWY 17L; AND MONITORED 118.90. SEVERAL PLANES WERE CONTACTING TWR AND THE CTLR'S VOICE SHOWED THE STRAIN. THEN SHE STARTED TO CALL THE N-NUMBER OF A PLANE BUT STOPPED PART WAY THROUGH IT; AS IF SHE WAS CALLING THE WRONG ONE; AND SAID OUR N-NUMBER; SAY CESSNA 12345. SHE TOLD US TO 'TAXI INTO POS AND HOLD' ONTO RWY 17L. I READ BACK THE CLRNC. THERE WAS NO ONE LINED UP ON FINAL APCH FOR RWY 17L. AFTER WE SAT ON THE RWY FOR A WHILE (TOO LONG; BECAUSE THERE WAS NO TFC AHEAD OF US ON THE RWY); THE CTLR SAID 'CESSNA XYZ (WHICH WAS NOT US) CLRED FOR TKOF RWY 17L.' NO ONE RESPONDED. THERE WAS NO ONE AHEAD OF US WAITING TO TAKE OFF AND NO ONE ON THE PARALLEL RWY WAITING TO TAKE OFF. I THOUGHT; 'OH GREAT; SHE DOESN'T KNOW WHO WE ARE AND HERE WE ARE SITTING ON THE RWY.' THEN SHE CAME BACK ON THE RADIO; VOICE VERY ANXIOUS; 'CESSNA XXY IS THAT YOU ON THE RWY?!' I RESPONDED; 'CESSNA XXY; AFFIRMATIVE; WE WERE CLRED POS AND HOLD.' SHE CAME BACK WITH; 'YOU WERE TOLD TO HOLD SHORT!' I WASN'T GOING TO ARGUE WITH HER BECAUSE I KNOW WE WERE CLRED 'POS AND HOLD;' PLUS MY PAX HEARD THE SAME THING I DID. SUDDENLY; A DIFFERENT CTLR GOT ON THE FREQ AND CLRED US FOR TKOF. SOMEONE BEHIND US WAS TOLD REPEATEDLY TO 'GO AROUND.' CENTENNIAL IS ONE OF THE BUSIEST GA ARPTS IN THE COUNTRY. THERE ARE NUMEROUS SCENARIOS (LIKE THE ONE JUST DESCRIBED) THERE ALL THE TIME. THERE ARE PLTS OF VASTLY DIFFERENT EXPERIENCE LEVELS AND ABILITY. CENTENNIAL IS A TRAINING FACILITY FOR CTLRS (THOUGH THE CTLR IN THE ABOVE SCENARIO IS VERY EXPERIENCED AND HAS BEEN AT CENTENNIAL FOR A NUMBER OF YRS).