The most infamous pairing I always think of was Led Zeppelin's first US tour in 68/69 when they opened for Country Joe & the Fish.
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 “