My daughter, SIL and two grand sons flew home from a 3 year assignment in Germany. She related the following event.
Everyone got through the metal detector okay.... except, my 4 year old grand son. The TSA agent, got an anomalous scan of his carry on back pack. Seeing the diminutive stature of it's owner, the agent quizzed my grandson in a very friendly fashion.
"Is that your back pack?"
"Yup!"

"Could you open it?"
"Yup!"

"What do you have in it?"
"I have my blanky," pulls it out.
"I have my beafer," pulls it out (He can't say beaver.. it's stuffed.)
Opening the top of the back pack wide to show the TSA agent," and I have my trains!"

Each of the 12 Thomas the Tank Engine train cars had a magnet on each end.
"Oh, that's just fine, you can go."

Glad to see the TSA agents are doing their job.