What's so funny?

Mama was singing us Primary songs the other night before bed, miss buggy and I really like that, and she said the wrong words! She sang:

"I hope they call me on a mission....."
But I always thought it was:
"I hope they call me Mr. Efeman...."

Mama thought that was pretty funny. What's so funny about that? I actually think it is kinda funny too, but I don't like that she was right and I was not. Sometimes words in music don't say what you think.

-sister sue