In S9 E18, The Application Deterioration Leonard, Howard and Sheldon find out that the university requires 75% ownership of their gyroscope patent. There's no explanation as to how the military was able to fund the project, and whether or not the university still received their portion of the contract.
In this episode, Amy mentions wearing a purple satin dress with a sweetheart neckline for the wedding. In The Conjugal Conjecture (2016), Amy's dress is purple but it is neither satin nor does it have a sweetheart neckline. It is a lace pattern & the neckline is too high to be classified as sweetheart.
Penny is correct when she jokingly says her "second marriage" would be to Leonard. Penny's drunken marriage to Zach was annulled in Season 7 Episode 9 "The Thanksgiving Decoupling" which means legally, the marriage never existed.
Leonard's mother is upset that she was not invited to his and Penny's wedding. However, in a previous episode The Celebration Experimentation she thanks Penny for not inviting her to the wedding in Las Vegas. However, given that Leonard's mother was actually upset she might've used sarcasm.
Throughout the series, it is mentioned that Leonard has a brother and a sister. There is no reason mentioned for their absence, while Penny's brother is attending.