More correctly, this sentences would be written "Is what's-his-name still working there? "What's-his-name" is short for "What is his name", and is used when the speaker can't remember someone's name. (If the person whose name is forgotten is female, it becomes "What's-her-name".) Normally both people involved in the conversation know the person being spoken about. Sometimes it is followed by a description, to help the person you are speaking to figure out who you mean. Example: "Is what's-his-name, the man with the red hair and freckles, still working there?"

"What's his name" means "the guy whose name I can't remember but you know who I am talking about."

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