Slaying metaphors

Sarah just said she was going to finish her math lesson in "one fellow swoop."  I laughed.  She said, "What's so funny? You say that all the time."  I said, "It's one fell swoop, not fellow."  She came back with, "Well, I'm going to kill two birds with one fell swoop, because I'm going to do my math lesson and color my book."  She was coloring the yellow butterfly on her book as she said that.  Noah said, "You're coloring that butterfly fellow with one yellow swoop!"  What a joy they are sometimes!