The Flash Season 2: 28 Easter Eggs & References You Might've Missed

25. Excelsior!

When working on the Speed Cannon, Professor Stein gets pretty excited when he has the problem fixed, and let's out a rather notable phrase: "Excelsior!"

Anyone familiar with comics, or comic book movies, will know this to be the catchphrase of Stan Lee, the legendary Marvel writer who created a number of their iconic characters.

Although DC and Marvel are rivals on page and screen, the presence of Lee isn't entirely unprecedented, as he did write a series of one-shot comics for DC under the Just Imagine banner, including The Flash. It also calls back to the Season 1 finale, when it seemed Stein was about to shout out 'Excelsior!' then.