Doctor Bellows tells Harry Huggins that a few weeks earlier Major Nelson had $3 million in his Christmas Club fund, and that it once snowed on Nelson's house alone, in July. These are references to later season 2 episodes 15 and 4 respectively, which aired 3 months later and a week later. The broadcast order of the episodes is obviously not the order in which they were written and filmed.
Mr. Huggins repeatedly refers to NASA and the Internal Revenue "Department" (sic) as different branches of the government. NASA and the IRS actually belong to different departments of the same branch -- the executive.