So was it Dan who played Monster Vigo or…?
Good question… might be, the problem is they used prothetics so it’s inconclusive from watching the TV if it’s Aykroyd or Wilhelm.
If I had to venture a guess between Dan and Wilhelm… I’d say it was Dan, because they don’t have the same build. It wouldn’t have looked like Dan if Wilhelm did it. And Dan seems to like doing “extra” stuff like that.
Yeah, i’ve thought the same thing and have paused it a few times in the past, i’m prrretty sure it’s Dan Aykroyd in makeup. His facial features seem recognizable, especially his eyes. I offer more support in the fact that they zoom in on Dan’s eyes when he’s being hypnotized by Vigo. Also, plot wise, it would only make sense that Ray’s body would be possessed by the spirit, because the spirit needed a body, such as Oscar. At least that’s my logic behind it 
Well even just from a standpoint of making the movie, it makes more sense for it to be Dan in the makeup, because if it was Wilhem, it would have looked like Wilhem being… Well, Wilhem. But it looks like Dan trying to look like vigo, lol. Make sense? No? Then my work is done here…
It makes sence that it would be Ray after he was possesed but Monster Vigo showed up before he took over Ray.