20 lbs in 3 months.

[Simplytoby]

Does anyone have a great three day work out to accomplish this goal? Also, a decent meal plan as well. I know that's a lot of crunching. But I'm up for the challenge. Include supplements as well. I'm a firm believer in supplements.

[jamesxvx]

Are you talking lean muscle mass or just mass in general?

[Justin Morgan]

First question is how much weight can you lift for your squat (below parallel), dead lift, bench press, Bent over Row, and Military Press?
Dorian Yates was only putting on 5-6 pounds per year and he was on more drugs than the South side of Chicago. If you've never lifted before, or are (de)trained then you might be able to put on 3-4 pounds/month for a month or two. But more than likely you are going to be in a calorie surplus and are going to be putting on fat as well. If you are counting fat you could probably put on 20 pounds in 2 months, or at least I could.
Supplements like creatine and powdered proteins will help you retain water and gain weight that way, but apart from water retention and bloating, no there is no magic pill that makes you grow muscle faster. Supplements help if your diet is deficient. Diet would be the best option though.