In the 1970's, I saw Journey open for Emerson, Lake and Palmer -- Journey was not well-received. Also saw Little Feat open for Electric Light Orchestra -- another odd combination but not nearly as poorly received.
Interesting/unusual concert pairings.
The Who as openers for Herman’s Hermits. Pretty much a failure. John McLaughlin and the Mahavishnu Orchestra opening for Zappa and the Mothers. Worked so well I attended in Milwaukee and Boston. McLaughlin and Zappa call and response noodling was spectacular. Roger Daltry did not join Peter Noone for a duet of, “Mrs. Brown you’ve got a lovely daughter “