E and the Tinkerbell Underpants

Everyone believes their child is the cutest, smartest, most talented child in the world.  I firmly believe my three year old and one year old are tied for the "most spirited".  I am attempting, for at least the third time, potty training.  This absolutely 110% is psychological warfare in our household.  Our family and friends have nearly been alienated by all of the pee pee poo poo potty talk.  I armed myself with positive reinforcement tools, ridiculous articles on how to train of off google, and enough diet coke to last through nuclear winter.
The first half of the day was perfect.  We set our little timer, went to the potty every hour, earned our rewards, signed off our chart.  It was actually kind of fun.  Then E decided she didn't like her tinkerbell underpants and wanted the brown haired fairy - so she peed, right there in the entry way - took off her underpants, handed them to me and asked me for "the brown haired underpants."  The combination of the truly disturbing nature of her verbage - the fact that she peed on the floor to get new underpants floored me. This went on for the rest of the afternoon, about every hour, just before our pee pee timer went off .  She just didn't like that fairy on her butt.  Why would you want any fairy on your butt - the fact that there are cartoon underpants at all is kind of alarming. What kind of long term effect would there be if I told her she can't pee pee or poo poo in her underpants because it will get pee pee and poo poo on the whatever characted I paid an extra two bucks to be on her underpants?  Can you tell I am about to lose it over the potty training.
We keep going, day by day.  She mad it through the museum with no accidents all day.  Got home and was up to her same tricks again . . . . oh how I love that little girl.