If songs give him powers...

[Kurisu]

What would mashups do to him?

(Treat it like wild magic?)
_____
DEATH is Certain. The hour, Uncertain...

[Cobalt Greywalker]

I'd expect them to work like any other song. The FAQ does say different versions of songs give Doug varients on the same power. And while I doubt it, you
could possibly get a two-for-one deal out of the mashup (depending on how much of each song's words are included), but it'd have to be one hell of a
good mix.

[Bob Schroeck]

A good mashup might even give him a completely different powerset, depending on what kind of "message" is in the fused lyrics.
-- Bob
---------
Then the horns kicked in...
...and my shoes began to squeak.

[Wiregeek]

f'rex,

OHH, YE-EEE-AH I tell you something
I think you'll understand
When I say the something
I want to choke your band!

I want to choke your band! I want to choke your band!

You'll say, "PLEASE! Don't tread on me!"
But I'm fuckin' pissed off, man!
For C.C.-no mercy
Cuz he'z in a hair band

Woah, let me choke your band! I want to choke your band!

And when I punch you I feel happy inside
It'z such a feeling, let the light-a-ning ride
Lightning ride, lightning ride

YEAH, YOU! Here'z your warning
That I wont take your glam
White Lion dead by morning
I want to choke that band!

I want to choke your band! I want to choke your band!

And when I punch you I feel happy inside
It'z just the flowing of your blood, you can't hide
You can't hide, you can't hide

YEAH, YOU! Here'z your warning
Wont take your fuckin' glam
Now Warrant'z dead by morning
I fuckin' choked that band!

I want to choke your band! I want to choke your band!
I want to choke your ba-a-a-po-o-seur band!!

could easily be interpreted to be an AoE Taunt, with the aggro target being the current live band playing...
"No can brain today. Want cheezeburger."
From NGE: Nobody Dies, by Gregg Landsman
http://www.fanfiction.net/s/5579457/1/NGE_Nobody_Dies

[robkelk]

Or perhaps it shuts off the current power of any other meta in the AoE who gets powers from music, by stopping the music.

Not a particularly useful effect... unless and until the mythical "Praetorian Doug" shows up.
--
Rob Kelk
"Governments have no right to question the loyalty of those who oppose
them. Adversaries remain citizens of the same state, common subjects of
the same sovereign, servants of the same law."

- Michael Ignatieff, addressing Stanford University in 2012

[Glidergun]

Or compare T. Rex's Get It On with the Kleptones' Get It On The Long Hard Road. Exact same vocal track, incomprehensibly huge difference on
delivery.