The weird theory, which has cropped up repeatedly throughout Trump's term in office, suggests that a body double for Melania accompanies the USA president at certain events, most recently a visit to survivors of a tornado in Alabama.
"They are only getting more deranged with time!" said Trump.
Co-host Brian Kilmeade remarked as an aside, "There's no one that has the president's back like the first lady".
Winter Storm Brings Heavy Snow and High Winds Across Central US
For the Dakotas, Nebraska, Montana, Wyoming, and Colorado, a blizzard warning was issued by the National Weather Service. The Lower Mississippi Valley and southern Plains will experience thunderstorms with heavy rain and flooding.
Popular US talk show The View also weighed in on the Fake Melania talk, and were later criticised by Stephanie Grisham, a spokesperson for Melania.
However, co-host Abby Huntsman did object to the segment at one point saying, "I think Melania's a handsome woman", and that she didn't like spending time on the topic. Hosts of the ABC programme debated whether an impostor had travelled with Trump. "Look how short she looks". "Sorry", Behar said of one photo.
"Yesterday's show went beyond the petty, mean-girl spirit that we've grown accustomed to", she added. "People died, people lost family, people are hurting in Alabama", Grisham said Wednesday in an email. "She's handsome, and we're doing this in jest".
Fox & Friends co-host Ainsley Earhardt said it was "so hypocritical".
"But does that make it better?"