A fine marathon to be sure. The crazy thing is they probably could've done a marathon of just panel shows.
The numerous episodes of What's My Line? featuring both Arlene Francis and Martin Gabel on the panel. The two instances in which the significant others of the members on the panel served as Mystery Guest. Betty and Allen's mystery guest appearance after their marriage (with a great line by Betty) and their appearance as panelists, Jayne Meadows appearing as a Mystery Guest after her and Steve's marriage. Lucy and Desi and George and Gracie also come to mind. There is also tons to draw from both I've Got A Secret and To Tell the Truth.
It makes me look forward to Valentine's Days to come.