This week marked 38 years since John Lennon performed at his last concert, when he joined Elton John onstage to perform "Whatever Gets You Through The Night" at MSG (all because he lost a bet). But that wasn't actually his last live performance, which came at the "Salute To Sir Lew Grade" at the Waldorf Astoria Hotel, on April 18th, 1975. Lennon, decked out in a red jumpsuit, was joined by eight-piece backing band Etcetera (who wore bald caps with two-face masks) to perform "Slippin And Slidin" and a very nice, acoustic guitar-strumming version of "Imagine." Watch below.
You'll note that Lennon changes the line in "Imagine" from, "No religion too" to "No immigration too" here, a reference to his green card woes at the time (he finally got it on July 27th, 1976). Below, you can also see Lennon's second-to-last TV performance, taken from The Old Grey Whistle Test—that includes an iconic clip of "Stand By Me," and "Slippin and Slidin." The performance were shot in NYC while Lennon was recording Rock and Roll; according to lore, Lennon missed Britain so much during this period (he couldn't visit because of the green card situation), he asked for English chocolates instead of money as payment from the BBC.
Finally, below you can watch the last TV interview Lennon gave, which came on April 8th, 1975 on The Tomorrow Show.