This is great! IMO, best work by Itaoka so far.
 
maybe Morimune? (I'm not really sure)
Interview with director
http://i.imgur.com/tT16GNv.jpg

Bear VS DokidokiTeam hiroki_morimune
MechaBear VS Black&White nishiki_itaoka
This is just a guess, but did Shuichi Ito work on the movie? It kinda reminds me of his stuff.
 
According to an interview in Animato! Issue #26: http://www.worldsfinestonline.com/WF/batman/btas/backstage/animato/

"TMS did the best animation of the series for this episode. The second part had maybe six retakes on the whole show, which is incredible," said producer Bruce Timm. "The first time we saw it in the editing room, we couldn't believe how beautiful it was. It has all those transformation effects that only TMS could do. It was after these two episodes that we decided that any two-parters we did would have to be done at the same studio." Timm had a theory why TMS did such a good job, which he felt resulted from Warner Bros' demand that they redo the opening sequence for the series.

Noted Timm, "I think when we shipped them 'Clayface,' they said to themselves: They think they know everything, but we'll show them how do do this show. We'll change Batman's colors. We'll do special color key treatments on the villains when they're walking over the green vat. We'll blow them away.' If that's their revenge, thank you for proving us wrong. I was so happy with that episode." "The sequence where Daggett and Germs are walking over that green vat, those characters look like they're three-dimensional. They look like they're rotoscoped. When Daggett slowly turns toward the camera, the shadows really wrap around his face. It's as if they're real! They did all those colors themselves. We couldn't even ask for those colors if we wanted to. They aren't even in our palette. They had to specially mix those colors." Shirley Walker, supervising music composer for the series, found the task of scoring this episode quite a challenge. "It was demanding story-wise," said Walker. "There was so much going on. I was so proud of it that I submitted it for Emmy consideration, and that's the one that I got a nomination for.""
 
sakugaku said:
IG is really terrible at coloring. This scene is so dark, it's a struggle to watch this just like Okiura's Arise scene.
Uhm. This OAV was produced by BONES and they're outsourcing coloring to studio Wish (Bones have their own color designer/checker, though -> http://puu.sh/aBkSJ.png ).
 
 
 
I love how the animator was able to make a smooth fight scene without sacrificing Shin-chan's unique look.