I thought the same, but that specific scene, it wouldn't make sense to use 3D models only for those 5 seconds if all that was of importance in that shot was the point-like effect of the entire image. You need to see the video version of this to see that it is a 3D scene, the shading is just too perfect on them, specially Marge's dress, it looks like cloth animation.

I found the video: https://www.youtube.com/watch?v=nf6dp4k-gmc&t=167s