可以，_______ Mr Smith and his wife in the room. 应该是强调句的省略形式，完整的句子是 It is Mr Smith and his wife (that / who...) in the room. 该句型一般用于强调句，例如：
It is the students that make me sad.
在强调句子主语时，强调句型结构不变，主语和其后的谓语搭配一致就行，又如：
My favorite food is dumplings.
主语 My favorite food 为不可数名词与谓语 is 搭配一致，表语为复数并不影响前面的 is。