Has there ever been a case throughout the history of congress?

Question

Where a seated member of the senate or the house of representatives has had to appoint someone to speak on their behalf?

Answer 1

Like if they were deaf, and needed an interpreter? I suppose that's possible, but I don't ever recall hearing about anybody needing a vocal representative.

If you mean to "fill in", Congressmen can't do that. You need to be an elected representative to be on the floor, and especially to speak.

A few times in history, a governor has needed to appoint a temporary Representative or Senator to serve in Congress, until a special election han be held (this happens when a Congressman dies, resigns, or is booted out.) The governor can also take his spot in Congress temporarily, if he/she desires.

Obviously, the last part is an exception to the second paragraph.