...a time for scootering...

This evening I was sitting on the coach, enjoying my Christmas break, watching the latest Netflix that had arrived in my mailbox.
One of my roommates was home, and downstairs in her room.
As I was watching, I thought I heard quiet knocking, as if someone was at our door.  But I didn't answer.  I didn't want to be interrupted.  Plus, we have a doorbell.  So I figured if someone really wanted to be let in, they'd ring it.
About 5-10 minutes later there was a LOUD knocking at my door.  This time I got up.
I was greeted by three young men (don't worry, I know all of them).
When I opened the door, they proceeded to ride their scooters into my house and then back out to the door step.
One was wearing a "futuristic" coat with snazzy belt.  Another was wearing a plastic bag like a backpack (you know, arms through the handles).  The third was sporting multiple "grandpa" sweaters (that's right, multiple), fingerless gloves, and long socks on the outside of his skinny jeans.
As we commented on the grandpa-like attire of the third (minus the skinny jeans of course), Plastic Bag
Boy says:  When Skinny Jeans Boy is a grandpa, I wonder what Futuristic Boy will be like.
Before roaring in laughter, we all pause awkwardly and Futuristic Boy says:  Uhhh, I'll be a grandpa.
(Of course Plastic Bag Boy actually used names, but I like to keep things anonymous.)

As I type this out it doesn't seem nearly as funny as it did in real life.  I mean, Plastic Bag Boy could have just said:  I wonder what Futuristic Boy will be like when he is a grandpa.

Did I just take away any humor that was remaining?

Well, in case I botched this time to laugh, here's a picture of a scooter like the kind they rode inside my house:

Oh yeah, and they said that was the only time they had knocked.  The mysterious quieter knocks (which my roommate also heard) before the guys arrived remain just that:  a mystery.