Tokyo - Emperor penguins looked up in awe on Friday as Tokyo's main zoo unveiled its latest addition - a giant penguin said to be suspiciously close in height and weight to a human.

"A great discovery!" blared the special news release by the Ueno Zoo, saying the Tonosama (Lord) Penguin was 165cm-tall and weighed 80kg.

As the cameras rolled, the real penguins rose their beaks and gazed up at the purported Lord - but then walked away disinterested when he took off his penguin face to reveal himself to be zoo director Teruyuki Komiya.

The press release - which stressed the newly discovered animal would be unveiled on April 1 - said the giant penguin's favourite food was "white fish meat with soy sauce."