Former Rep. George Santos (R-N.Y.) made a surprise appearance Thursday at the State of the Union address, where he announced he plans to primary Rep. Nick LaLota (R-N.Y.) just months after being expelled from Congress.

Why it matters: Santos — who was spotted wearing a rhinestone collar and silver shoes in his dramatic return to the House chamber — was not welcomed warmly by the many former colleagues who voted for historic ouster in December.

• The House expelled the New York Republican in a 311-114 vote following the release of a scathing ethics report that detailed a "complex web of unlawful activity."
• Santos — who has also pleaded not guilty to federal fraud charges — has argued he wasn't provided due process before becoming just the sixth member of Congress in U.S. history to be expelled.

Between the lines: As a former member of Congress, Santos still retains floor privileges — technically allowing him to attend the president's annual address. House rules would bar him from walking onto the floor if he was convicted of a crime.

What they're saying: "New York hasn't had a real conservative represent them since I left office arbitrarily, thanks to RINO, empty suits like Nick LaLota," Santos tweeted in his announcement, targeting one of the freshmen New York Republicans who pushed to expel him.

The big picture: Republicans lost the February special election to fill Santos' seat to Democrat Tom Suozzi — prompting gloating from Santos and some regret from Republicans about thinning their own majority.

Flashback: This is not the first time Santos has made a splash during a State of the Union. Ahead of last year's speech, Santos had a tense public exchange with Sen. Mitt Romney (R-Utah), who said the serial fabulist didn't belong in Congress.