If you think the one thing missing from all the opinion-spouting over the Janet Jackson scandal has been some snarky commentary from ''American Idol'''s outspoken Simon Cowell, you're in luck. Cowell, who's accustomed to working alongside the Randy Jackson who is not Janet's brother, will be joining Janet as a ''special guest'' when she serves as both host and musical guest this weekend on ''Saturday Night Live,'' NBC announced Tuesday. No word on whether we'll see an ''Idol'' spoof featuring Janet as her one-time choreographer Paula Abdul, or whether Cowell was recruited to take some of the burden of hosting and singing off of Jackson. But it can't be easy to do double duty on ''SNL''; only a handful of other performers have done it, including Paul Simon, the Rolling Stones, Ray Charles, Stevie Wonder, Dolly Parton, Garth Brooks, Sting, Jennifer Lopez, Britney Spears, and Justin Timberlake. Some of them probably could have used some help from Simon as well.