Clash of the 70s Titans

Despite the fact that the 1970's were responsible for a few gems (1. me, 2. the Eagles, and 3. that one episode of CHiPs where John skateboards in an empty swimming pool), they also produced some complete mysteries:

The best part of the clip is that I can't figure out whether they're playing this serious or for laughs. Maybe if Jessica Simpson would do another variety show, we could start understanding the cultural context for the wackiness that was the Donny & Marie Show.