For the record: this was all Max's idea, and his own original musical arrangement. The kid loves Pooh, and he loves Green Day, and he's been introduced to the concept of "mashups."
The rest is punk rock history.
Addendum and Explanation:
Several folks have asked what a "Mashup" is. For the uninitiated: it's when a dj edits two (or more) songs together, or puts the lyrics from one over the beats of another. When DJ Dangermouse combined the Beatles' White Album with Jay-Z's Black Album to make the Gray Album, that was a mashup.
Then folks who know what a mashup is wonder what makes the above performance a mashup. The answer is: nothing. It's not really a mashup. That's just what he called it (he knows the concept of "mashup" from Dean Gray's "American Edit," a mashup re-mix of Max's favorite album, American Idiot). It's actually just the Pooh theme song, sung as punk rock.
The lyrics (for those without toddlers, who may have forgotten):
Deep in the Hundred Acre Wood
Where Christopher Robin plays
You'll find the enchanted neighborhood
Of Christopher's childhood days
A donkey named Eeyore is his friend
And Kanga, and little Roo
There's Rabbit and Piglet and there's Owl
But most of all Winnie the Pooh
Winnie the Pooh, Winnie the Pooh
Tubby little cubby all stuffed with fluff he's
Winnie the Pooh, Winnie the Pooh
Silly willy nilly old bear
Last note: yes, his "microphone" is my new cane, which I've been graced with for spraining and possibly breaking my knee.