It's the saying to be used when somebody claims that solved some problem. You approach their solution and find a mistake or omission of taking into account a pivotal issue.
1)Dude, did you get the tickets to the Teacups in Flowerland concert?
2)I MADE UP MR. FINKLESTEIN, NOT STRAY! HE'S MY CREATION!!!!!!
3)Am I a teacup in flowerland?