So the other day, I was taking my youngest to school, and passed by the local movie theatre, where the marquee read: "New Moon" and "Old Dogs".
It made me smile and got me thinking about the saying, "You can't teach an old dog new tricks."
A quick internet search shows that this sentiment has been around a LONG time:
The dogge must lerne it when he is a whelpe, or els it wyl not be; for it is harde to make an olde dogge to stoupe.
[1530 J. Fitzherbert Husbandry (ed. 2) G1V]
Time travel not withstanding, all I have to say is J. Fitzherbert never met Cesar Millan...