Dair Haired Warrior said Nefarious would only cameo in Qwark's "Claim to Fame" commercial. He said Insom hinted at it.
When, where, how? Besides, there are photos of Armin Shimerman in the studio performing the role, on one he's doing his evil laugh, so I think there will be a little more of him than just a cameo in a commercial… But even still, Lawrence would have to stand next to him in that commercial for at least one second.