"Jim, what is this device?"
"Huh? Spock, you don't know what a slinky is?"
Spock quirked one eyebrow up. "A 'slinky'? I do not understand the purpose."
Jim opened and closed his mouth a few times, before letting his palm meet his face. Spock was once again confused. This was what Jim often did when Spock did not understand some human ritual.
Finally, Jim spoke.
"It's a toy, Spock. It's to have fun with."
This only confused Spock more. He stared at Jim or a while, until the human boy heaved a sigh, stood up, and looked down with a grin.
"Come on, Spock I'm gonna show you how to use a slinky!"
He reached down and grabbed Spock's hand, once again ignoring the green blush that erupted on his friend's cheeks, and pulled him along.
They ended up spending the rest of the day "having fun" with the slinky device. Finally, as the sun was setting, Jim turned to Spock and said
"So? Do you get it now?"
Spock hesitated for a moment, and replied "Yes, I believe so." Jim grinned, and the grin was quickly replaced with a look of annoyance when Spock followed it with "I would be interested in understanding the scientific principals behind this device."
Kirk just groaned, and walked away, leaving Spock to wonder what he had said now.