Silver Skrull

When numerous heroes of Earth traveled to a moon of Saturn to mourn The Death of Captain Marvel, a spy was among them.

Sent to gather information about the heroes, a shapeshifting agent from the Skrull Empire came disguised as Devil-Slayer. After seeing that the real Devil-Slayer was also there, the Skrull changed form to masquerade as the Silver Surfer instead.

The real Silver Surfer, meanwhile, was still trapped on Earth at the time. The former herald to Galactus only learned of the charade in when he encountered the Skrull double in Silver Surfer #14 (Volume 3).

Silver Surfer. Vol. 3. No. 14. August 1988. "Silver Mirrors!" Steve Englehart (story), Joe Staton (pencils), Joe Rubinstein & José Marzan (inks), Ken Bruzenak (letters), Tom Vincent (colors), Craig Anderson (editor), Tom DeFalco (editor in chief).