Who IS that man?!

Ibdb credits Michael Anthony as the Hotel Desk Man, Oscar, but in his one line in his first scene he SOUNDS just like the wonderful Walter Slezak (the back of his head sure looks like him)! In later scenes "Oscar" looks like he could be another man, but with a fair resemblance.

Slezak's credited with working with Cary Grant on Once Upon a Honeymoon (1942) and People Will Talk (1951); could it be that he did this tiny part - or part of it - credit and check to British actor Michael Anthony as an in-joke/favor? I'd be more suspicious if Slezak had worked with Donen, but I can't find any record of that.

Slezak, a studio regular, was spending most of his time in television in 1958, but I suppose he might have been in England when the Desk Man's first scene was filmed - though not actually possessing a work permit for British work that year.

Anybody know? Was it all actually Michael Anthony?