Oscar's understudy performer?

I was just wondering, we know Matt is the understudy for the Bird, but does anyone if Oscar has an understudy performer?

Also, in general, does anyone know if other characters have understudies, and if so - who?

Presently, Jim Martin performs the puppetry for Oscar (specifically, if Big Bird and Oscar are in a scene together), but Caroll dubs the voice; however, it's my understanding that Johnny T. voiced Oscar for that 4D thing.

Johhny T. didn't do his voice; I've seen it and it's Caroll. I'm pretty sure he did Big Bird too, but I think Matt did his voice during a song.

Actually, Matt performed Big Bird throughout the whole show, at least in the original filmed version; when the attraction finally made it to the US 6 years later, Caroll re-dubbed all of Matt's dialogue (except for the opening song). I know this because I saw a preview clip of the main show intro (the one with Big Bird looking out at the audience from the Sesame Street logo) online years ago, and it was indeed Matt. With that said, it'd make sense that John T. was doing Oscar.