It's finally the moment fans have been waiting to see. Gotham, four years after its inception, has introduced Joker to the mix.

A Long Time Coming

After a long wait, loaded with teases and red herrings, Batman's greatest nemesis was finally revealed in all his glory. Although, in typical Gotham fashion, it wasn't in the manner fans had anticipated.

Viewers have been speculating about The Joker's identity for a while now. Last year, co-executive producer Bryan Wynbrandt confirmed that it would not be hot favorite Jerome Valeska, played by Cameron Monaghan.

Last week's episode saw Valeska tracking down his twin brother, Jeremiah, with the intent of driving him insane. This week found Jerome perishing in a hail of gun-fire via Ben McKenzie's Jim Gordon, which leads him to fall to his death from a rooftop. 

Right In Front Of His Face

Twin Jeremiah, understandably, takes the news of his brother's untimely death to heart. He doesn't have much time to mourn, however, as a mysterious package arrives that, upon opening, douses the young man in a strange gas.

The gift, containing a jack-in-the-box, purports to be from Wayne Industries, but it's the final act of Jerome's revenge plot, meant to punish his brother for all the years he spent as an outsider. As a result, Jeremiah turns into the greatest villain Gotham and Batman have ever seen - The Joker.

A message from his brother plays before the transformation occurs, spelling out exactly what Jerome intends for his sibling.

"Hello, brother. Didn't think you could get rid of me so easily, did you? See, my days were numbered but you, oh, you can continue on for me. Be my ultimate revenge. So, calm yourself. Breathe it in. This gas was a special mixture I made, just for you. Something to finally set you free. It's time to have some fun. Burn it down, brother. Burn it all down," he intones from beyond the grave.

A Terrifying Transformation

The gas, originally intended for the denizens of Gotham, contorts Jeremiah's face into a Joker-esque grin. He writhes in pain until his cries turn into maniacal laughter.

The moment gave actor Monaghan, who plays both brothers, the chance to go all-out with the character made famous by Jack Nicholson, Heath Ledger, and, in animated form, Mark Hamill.

The argument could, of course, be made that Jerome is actually the real Joker because, aside from driving Gotham to the brink of madness, he also created the Clown Prince of Crime through his brother.

Jeremiah is perhaps more dangerous due to his background as an academic, and his close relationship with Wayne, who gave him a grant thanks to his designs for the city.

Now that he thinks the billionaire playboy targeted him, Jeremiah has one more reason to target Bruce Wayne/Batman than his brother did. Season 5 is sure to be explosive.

Gotham airs Thursdays at 8 p.m. ET/PT on Fox.