"Show and Tell..." joke

The teacher asked the students to bring one electrical appliance for
"Show & Tell," and the next day every kid had something.

The teacher asks Wendy: What did you bring?
"I brought a Walkman."

"And what is it for?"
"You can listen to music with it!"

"That's nice Wendy. What did you bring Kenny?"
"I brought a' lectrical can opener, it opens cans!"
"Well done, Kenny.

Umm, Johnny, I see you didn't bring anything!"
"Yes, I did. It's in the hall."

So the entire class goes into the hallway.

"Umm, Johnny, what is that?"
"It's a heart/lung machine hospitals use to keep your heart going."

"Whoa. What did your father say about you bringing this?"

"He said,' AAAARRRGGGH!!!'"