On the boxes of Cheerios the back panel is celebrating the "50th Birthday" of Bugs Bunny who was "born" on July 27, 1940.
Since 10 year old Sheldon's birthday is February 26th, 1980 making the point of time in this episode 1990, the year of Bugs Bunny's 50th.
The antenna that Sheldon and Dr Sturgis have set up in Sheldon's house is a "magnetic loop". It is most notable for being very efficient for it's small size, as most other shortwave antenna designs would be much larger and cumbersome.
According to the breakfast cereal supply that Sheldon sets up in the garage, at one serving per person, he was prepared for approximately 100 people to attend his party. Unfortunately, he only had enough milk for 50.