Sir John Key was spotted sitting in Parliament on Tuesday afternoon.
The former Prime Minister was sitting on a side bench in the House and could be seen on Parliament TV's camera, speaking to National MP Chris Finlayson.
Mr Key listened as Speaker Trevor Mallard opened Question Time, where MPs have the opportunity to ask Ministers questions.
A National Party spokesperson told Newshub he was in Wellington on personal business, and "called in to see his former colleagues and thought he'd check in on their progress in the House".
The spokesperson said he was "impressed with the focused and effective Opposition - something he never saw during his time as Prime Minister".
A few people on Twitter pointed out that they'd spotted him.
Mr Key resigned from his position as Prime Minister in December 2016 and was replaced by Bill English.
He made his valedictory speech to Parliament in March of this year.