As far as 100th episodes go, "Arrow" nailed it. Many fans were worried the episode falling within the larger "Invasion!" crossover arc would leave no room for a proper celebration of "Arrow" -- but that wasn't the case at all.

Instead, fans got what was essentially a love letter to the early days of the show and the people who populated the then-Starling City. From the Queens, to Laurel -- to even Deathstroke and Malcolm Merlyn -- the gang was all there, and it felt like a very good reason to celebrate. They aren't the only ones who showed up for Oliver's imaginary marriage to Laurel, though.

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Much to our surprise, Roy and Tommy made the cut! Sure, they were in hologram form, but Colton Haynes (Roy) and Colin Donnell (Tommy) got the chance to make their presence felt in the episode thanks to some pretty interesting visual trickery... which wasn't always planned.

"That beat was not in the original break of the episode. Honestly, I can’t even tell you where that idea came from," executive producer Marc Guggenheim reveals. "It was just, I was writing that scene where Oliver goes back, and it just popped into my head that basically all the actors that we can’t get -- at the time I didn’t know who we could get and who we couldn’t -- I’m like, this is a way we can get them."

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From there, Guggenheim let the visual effects team at Zoic take over. "Zoic handled those shots and they did an amazing, amazing job, particularly with Colin and with Colton, because we couldn't reshoot them," he explains. "We had to take them from old episodes and roto them out and put them into this. It was hard, obviously, because they had to work with pre-existing footage. Yes, they had 99 episodes to choose from, but it was a lot harder than it makes it sound. They did an incredible, incredible job, as they always do."

So while Haynes and Donnell couldn't shoot new footage for the episode, they still got their chance to shine. Given how heavy on "Arrow's" past the 100th episode was, it's only right they be paid homage. After all, an "Arrow" without the likes of Roy Harper and Tommy Merlyn is not something we want to imagine.

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Hopefully this isn't the last fans will see of them. While bringing Donnell back is a bit tougher due to his character being dead and starring on a little thing called "Chicago Med" -- and kudos to the writers, for the shoutout about Tommy working in a hospital now -- there's no reason Roy can't pop up now and then. After all, given how tough things have been for Thea lately, she could use a friendly face.

Here's to the next 100 episodes, "Arrow." Who knows what kind of nonsense Oliver and the team will be fighting then.

Posted by:Chris E. Hayner

Chris E. Hayner is equal parts nerd, crazy person and coffee. He watches too much TV, knows more about pro wrestling than you do and remembers every single show from the TGIF lineup. You may have seen him as a pro-shark protester in "Sharknado 3." His eventual memoir will be called "You're Wrong, Here's Why..." TV words to live by: "I'm a firm believer that sometimes it's right to do the wrong thing."