My husband and I live in Kentucky now (after living in Frankenmuth, Michigan), so when our daughter got married, my brother came here and performed the midnight ritual, except we did it at 9:00 pm because people around here don't party that late.
Custom is that at the wedding reception the bride and groom are each placed in a chair just before midnight. This German song is sung lead by one man, four men on each leg of the chair lift it for the blessing of the marriage. The chairs are lifted at least twice, once while they are bride and groom (before midnight), and a second time (after midnight) to note that they are now husband and wife. The funny hats are placed on them after the midnight stanza. The hats are attached by string with baby items like rattles, a pacifier, diaper pins, etc. to signify fertility.
I have never witnessed it, but some brides and grooms have fallen off or were tossed off their chairs. More than likely because of too much beer, which is very probable at a German wedding reception. At our reception in 1971, after the song, they carried my husband and I (while seated on the chairs) all the way to the bar and placed the chairs on it. It was at least fifty feet in distance.