Keith Olbermann, Joel McHale

E! Networks

As Soup loyalists are well aware, the McHale vs. Olbermann guest-appearance one-upmanship is a vessel that shows no signs of sinking. Now, after the beloved newsman’s recent, charged Soup appearance, McHale is picking up the gauntlet (and union scale) to step into the Countdown arena this very night.

The agenda is anybody’s guess. Behind-the-scenes, showbiz-hosting tidbits? Perhaps a frank discussion of Olbermann’s pet passion, Merkle’s Boner? Don’t miss it. Tune in to MSNBC at 5:40 p.m. PT/8:40 p.m. ET