Arrowverse Crossover: 10 Most Awesome Moments From 'Invasion' (Part 1)
9. Aliens!
It had already been revealed that alien race the Dominators would be the villain of the crossover, so it's not a surprise when they turn up on Earth in the early goings of this episode.
However, that doesn't mean it's not fun. As Barry goes to investigate the 'meteor', which is of course their spacecraft, he's quickly overrun by the alien species.
It's all a bit ridiculous, and is topped off when Barry manages to compose himself to yell "Aliens!" It's fun, silly, and does a good job of setting the tone for what's to come.