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The nerd / kiddie safe version of what is obviously 'WTF'...

Early origins of 'flagnar' can be traced back to the cockroach Scientist character from Monsters vs. Aliens exasperatedly uttering 'what the flagnar?'
Joe: Check out that guy pushing that hen up the escalator!
You: What the flagnar!?!
by CoaXygen July 10, 2011