Sheldon tells Kripke he doesn't want to end up in a MAD Magazine. The Big Bang Theory has been advertised on the back cover of some recent copies of that magazine.
Leonard is briefly able to control Sheldon by being strict and firm with him, and then hopes he will remember this for a next time. This is basically how Sheldon's mother controls her son when he gets stubborn.
Sheldon again shows his compulsive obsession with repetitions of three when he yells "Nobel, Nobel..", is then interrupted by Barry Kripke, and finishes with "...Nobel" afterwards, just like his signature door knock.
The "scale replicas" received by Howard and Raj actually have each other's haircuts.