They learn so much you don't expect

A few days ago Izaak began pantomiming talking on the telephone.
He would open up one of our cell phones and hold it up to his ear, sometimes just listening, but sometimes talking as well. Well, he's 13 months you say? It's completely normal for a child to have that down by now? ... well I'd agree, except: neither Alex or I talk on the phone in the "traditional" way... I always use a headset and Alex always holds the phone out in front of him with the speakerphone turned on...
So.
How did our dear boy learn to "talk" on the phone?
No Idea!!
*shrugs*

In this little video he even says "Hi"!!! (not 100% sure that was intentional, it could have been just a random syllable... he *waves* "Hi!" (and "bye") but he hasn't verbalized it yet that I am certain of (this being the closest).