With everyone knowing TCUN was stealing signs...this was the first thing I thought of. Apparently so did Coach Dykes... 

As per Yahoo..."TCU coaches, having gained information on Michigan’s elaborate sign-stealing scheme, changed many of their play-call signals before kickoff. However, head coach Sonny Dykes and the Horned Frogs staff had grander ideas than just changing signals. They pulled a fast one on the Wolverines.

They mixed in new play-call signals with old ones, using what one TCU staff member described as “dummy signals” in an effort to trick the UM staff. The dummy signals were old play-calls that had since been changed. Players were told to ignore the dummy signals and run the original play as called with the new signals." https://sports.yahoo.com/sources-tcu-knew-of-michigans-sign-stealing-scheme-prior-to-cfp-game-used-dummy-signals-to-dupe-wolverines-224848698.html?guccounter=1&guce_referrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_sig=AQAAABrbCx8Aga8cEHqhnjVHev9zB_6isZgNXwyYQIVtbY-ANJFi82TtSKo8i4FQpjfm5dVJqSa6GVzTQPOGEZ3UbPGmWht1pGVQfIv6PupMDcpMIkdkbYKMu8HqiAMGQm8akfY76YdZSmVVzTvhvuD3uPJpZR3feD5XqQTl8JYPygSY#:~:text=TCU%20coaches%2C%20having%20gained%20information,play%2Dcall%20signals%20before%20kickoff.