Jarvo - who has previously donned cricket whites and joined two England v India cricket tests and stripped down to Speedos to be an Olympic diver - told the Herald last week he'd wanted to be an All Black "because they are the biggest, best rugby team in the world".
He was originally planning to join the haka, perhaps unaware of its cultural importance. "I don't know the haka moves. I was going to do my own crazy moves."
But as the All Blacks were gathering to line up for the anthem, a steward walked from the bottom of the stands, up some stairs. The 33-year-old saw his moment to strip down and head to the turf. "I don't pause. If I act confidently enough, it usually works."
No one pursued him as he jogged, player-like, onto the field, and video shows one official was looking the other way as Jarvo moved behind him to join the All Blacks.
Jarvo's YouTube video shows Richie Mo'unga, Sevu Reece and Brad Weber all cotton on to him pretty quickly.
"When I got there, the players looked at me and looked at me. They didn't say a word. I was looking around. I think the thing that gave me away was my mask."
In Cardiff, he was on the field for about 35 seconds - and in the line-up for about 20 seconds - before a steward finally approached him as the national anthem was starting.
It appears it took even longer for security to react in Dublin.
