At one point, Porter reportedly yelled at a reporter about her outfit.
“It’s Batgirl!” she told Washington Post reporter Mike DeBonis.
"As House Democrats prepare to officially blow up their Majority with impeachment, @RepKatiePorter is prancing around dressed as Batman. This is how seriously these clowns are taking impeachment," the National Republican Congressional Committee tweeted on Thursday.
Steve Guest, the spokesman for the Republican National Committee, also took to Twitter to assail the lawmaker's decision to wear her costume on Thursday.
"Democrat Rep. Katie Porter is making a mockery of the House of Representatives," Guest tweeted. Alongside his tweet was a photo of Porter sitting in the Financial Services Committee.
Porter responded via tweet: "Taking my work in Congress seriously doesn’t mean I take *myself* too seriously. To my kids Luke, Paul, and Betsy, I’m still just Mom—seeing the Bat Signal on Halloween & putting on a goofy costume come with the territory."
"Of course Republicans, who love their criminal president, got triggered by a Democrat dressing up as someone who beats criminals to a pulp," filmmaker Adam Best tweeted.