Arrowverse Crossover: 11 Best Moments From Arrow's 100th Episode 'Invasion!'
5. The Easter Eggs
Arrow typically contains a fair few Easter eggs anyway, but they suitably went above and beyond in marking the occasion, with a number of nods and references to the past.
Of course there were all the obvious returnees, from Deathstroke to the CGI of Tommy Merlyn, but a few more subtle ones as well.
Explaining away Tommy's absence, Malcolm says he's working at a hospital in Chicago - a nod to actor Colin Donnell's role on Chicago Med.
When Oliver is trying to find out who the vigilante who saved him is, the police sketchings are the same as those used in Season 1. When he eventually finds his way to the Arrowcave, he quotes the voiceover that opens each episode, and Diggle responds with Season 1's "no one can know my secret."
Thea gifts Oliver a hōzen - the same rock he gave her in the pilot. When Robert wants Oliver to take over WC, he says give it to Walter Steele. Walter, of course, takes over after Robert's death - and becomes Oliver and Thea's father-in-law to boot.
They're just a few of the examples littered throughout the episode, which really helped pay homage to the previous 99 instalments.