During the two-hour show, TV newsman Steve Edwards presented a satirical report titled "Bad Judgment" that purported to reveal, using intercepted phone messages, judge Simon Cowell's "secret relationship" – which Cowell turned out to be having with himself.
In an ABC report last month, Clark, 23, revealed his claims about Abdul, mostly based on phone messages.
Wallace went on to call the Edwards-Cowell skit a "slap in the face."
Clark responded similarly after Abdul made a comedic appearance on Saturday Night Live earlier this month. Afterward, he announced that he had "explicit" and "incriminating" evidence of their alleged affair, though they have yet to surface. Clark claimed an alleged relationship with Abdul at the same time he was pushing a book and new CD.
For her part, Abdul, 42, has called the allegations "lies." FOX has said it would investigate the claims, but that Clark had not responded to requests for help in the investigation.