Final answer:
The character who says this line is from the movie Frozen.
Step-by-step explanation:
The character who expresses the line, "I'm not the heir, I'm just the spare. Forget it. I'm not making any sense. How embarrassing?" is from the movie Frozen. The character who says this is Anna, the younger sister of Elsa, the snow queen. In this scene, Anna feels overshadowed and unimportant compared to Elsa, who is seen as the rightful heir to the throne.