Mr. and Mrs. Quackmore

Mr. and Mrs. Quackmore are a duck couple visiting The Furchester Hotel in the episode "Furchester TV."

When they visit the hotel they immediately note the lack of a television in their room, causing Furgus Fuzz to fetch it from downstairs, unfortunately the TV's busted so Elmo, Phoebe, and Cookie Monster put on shows for them, until they tire the monsters out, and are allowed their own chance to "be on TV."

They speak in quacks, but also speak monster, which sounds exactly like English.