SOTO Mikey Pose
 

Since the early days of TMNT often featured references to old-school movies/actors, I've always wondered, is Mikey supposed to be doing a sort of Groucho impression here? Or is it just an otherwise odd pose?

http://i.imgur.com/AscjkiG.png

He's the goof, so he's pretending he can use his 'chucks to listen to the inside of the cannister.
In the UK the presence of the (banned) 'chucks on the poster meant that they had to colour swap the Turtles, and Mikey became Donnie to legitamise the science of it.

I can TOTALLY see that now. Never noticed it before. Good call!

Well I attempted a couple of searches to find the poster of Donnie doing the Mike pose but all I found was this:
It's a mirrored version basically. Perhaps you have the one with their bandanas switched?
(and yes, I did try typing Hero Turtles 2 the Secret of the Ooze)

Oh, is that what he's doing? Huh. Thanks!

Haha, I was always confused by his pose, myself. Good to hear another perspective on it. I thought it was just awkward posing for so long.

I never noticed that before... tiny nunchuck stethoscope.