Marvel's Agents of S.H.I.E.L.D. premiered last week to a strong audience, and an estimated 22 million people have already watched the first episode.

12.1 million viewers tuned in to watch the pilot episode on September 24, followed by millions catching up on DVR via online streaming.

The second episode will be airing tonight, titled "0-8-4." Be sure to watch the second episode online on ABC's site here.

The latest rumors on the second episode point to a surprise cameo guest!

The Avengers' Nick Fury may be making a surprise appearing in tonight's episode, and viewers will have to wait and see if this is true!

ABC teased the second episode with a promo posted on its Facebook page.

The promo states: "Don't risk the spoilers, stay to the very end." Then the promo quickly shows the eagle in the S.H.I.E.L.D. logo wearing an eye-patch – which has fans wondering if it is indeed Samuel Jackson who will be making a cameo appearance. Jackson's character Nick Fury wears a black eye-patch in the Avengers movie.

A Facebook message directly underneath the clip says: "Be sure to stay until the end of the credits on Tuesday. In true Marvel fashion, you never know what might happen."

The Agents of S.H.I.E.L.D. Facebook page has already amassed 1.3 million likes. The show had already reached a million followers even before its season premiere last week.

Episode 2 will see Phil Coulson and his agents travel to Peru to investigate an unknown object.

The television series is created by Joss Whedon, Jed Whedon, and Maurissa tancharoen, based on the Marvel Comics organization S.H.I.E.L.D. (Strategic Homeland Intervention, Enforcement and Logistics Division).

The cast and characters of the show are as follows:

Clark Gregg: Agent Phil Coulson who oversees S.H.I.E.L.D.'s main operations

Ming-Na Wen – Agent Melinda May, ace pilot and weapons expert

Brett Dalton: Agent Grant Ward, black ops specialist

Chloe Bennet: Skye, computer hacker

Iain De Caesetecker: Agent Leo Fitz, weapons technology specialist

Elizabeth Henstridge: Agent Jemma Simmons, life science specialist