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Williams, who plays the scheming Wilhelmina Slater on the show, is also keen to get veteran actress Lily Tomlin in for a guest role.
"I've always loved their comedic style, and they always play really interesting characters as women," she said, "so I would love them to come on and give Wilhelmina a run for her money."
Victoria Beckham, ex-American Idol contestant Katharine McPhee, Lucy Liu and Gene Simmons have all previously appeared on Ugly Betty.
Williams added: "We just recently had Christian Siriano from Project Runway - he's fabulous and he did a great job with Nina Garcia, who came as well. Gabrielle Union plays my younger sister, Renee, and she's been doing a great job."
