If it blasts off as expected this weekend, “Deadpool & Wolverine” is slated to rival the billion-dollar grossing “Inside Out 2” as summer’s biggest blockbuster.

For Ryan Reynolds and Hugh Jackman, this comes as the sweetest cherry on a cake that’s been baking for decades.

Jackman, now 55, was 30 when he was a last-minute casting for the first X-Men movie. The original actor had a scheduling conflict and had to be replaced.  It would be the Australian’s first Hollywood movie. Overnight, it launched him onto the A-list.

But there was a hitch, Jackman told the New York Times.  His paperwork wouldn’t clear Customs for entry to the filming in Canada.  Only when he moaned that this would cost him the chance to play Wolverine, all doors suddenly opened. Customs people are fans like everyone else.

Jackman’s returned for the 10th time to play the ultraviolent superhero – and it was that willingness that made this new movie possible.

Because Jackson had sworn he was done, as in really finished and so long, goodbye, to his career-defining role when he changed his mind in 2022. That suddenly made this all-star teaming a big screen reality.

Reynolds, 48, had been pushing for a Deadpool movie for over 10 years when in 2016, only after leaked test footage on social media made it obvious this could be some kind of monster hit, did his “Deadpool” movie get greenlit.

On a puny $58 million budget, Reynolds’ foul-talking burn victim scored $782 million worldwide.

Today, Reynolds credits the fact that they were underdogs – he wasn’t getting paid at one point – that kept the movie true to its semi-gritty roots.

In terms of personal history, these actors go way back.  It was “X-Men Origins: Wolverine” (2009) that Deadpool made his first appearance opposite Wolverine.

By that point Jackman was the muscle who ruled the roost.  Once, after they had wrapped for the day, Reynolds recalls muttering to Jackman he wished he could have had one more take on a scene they’d done earlier that day.

“Five minutes later, everyone is being asked to come out” – Jackman made it possible for him to reshoot. That left a lasting impression.

“I think,” the director Shawn Levy said at last weekend’s virtual press conference, “the Marvel Cinematic Universe is always at its best when it is giving us something we don’t expect — and this ability to surprise is the MCU at its best.

“We had an opportunity collectively to do the first R-rated MCU movie. And the first pairing of Deadpool and Wolverine!  Built into this was the chance to surprise, do something new and unexpected.”