Clark Gregg, who plays Agent Phil Coulson in Agents of S.H.I.E.L.D., and Hayley Atwell, the titular character of Agent Carter, are at it again with their musical brawl, but this time, they will give it everything they've got on the stage of Spike TV's Lip Sync Battle.

On April 18, Spike released a short preview of Gregg's final performance for the battle on April 21 in its YouTube page. And let us tell you now, you should not miss it as there is no doubt the two will pull all the stops to win the battle, even if they are playing for the same organization that "no longer exists."

The two agents have been battling it out in the musical department ever since their friendly dubsmash battle began in 2015, which eventually became a contest as well as a charity fundraiser between the two television series. Atwell gloriously won that round with the help of Captain America, Chris Evans, but it seems Agent Coulson wants a rematch and he is not going down without a fight.

In the 44-second preview, Clark Gregg channels his inner '90s teen pop star and lip syncs to Britney Spears' 2003 song "Toxic," complete with a flight attendant outfit.

Now brace yourself for Gregg's performance, but before you press that play button, let us just give you all a fair warning: you cannot unsee him in that flight attendant uniform.

Even Atwell could not stop herself from laughing when he went on stage. Are you ready to see it? Actually, you can never be ready for it. Just watch it below!

Did T.A.H.I.T.I. do this to Agent Coulson or is it The Hive making him do these things? At least we did not need a level 7 security clearance to see this.

For sure Atwell also has something up her sleeve for her own final performance, so we're definitely looking forward to that. After all, these two may be fighting for the same team, but when it comes to lip syncing songs, Gregg and Atwell are definitely rivals.