I may have posted this elsewhere.....
My wife screws up some lyrics horribly. But the funniest to me is a Beatles mix-up: "Ola di, ola da, my cousin...bra....la la la life goes on" (cousin pronounced coo-ZAHN).
I also had a cute one with my son. When he was between 2 and 3, and we'd give him baths, he'd like to have the radio on. Often, classic rock was the choice. And several times, when the Rolling Stones "Ruby Tuesday" tune came on, he'd sing along: "Goodbye...see ya Tuesday....."
I've screwed up a lot of lyrics in my days, too. One nice thing, though: I was a big fan for a while of the Cocteau Twins, and NO-ONE knew the real lyrics except Liz Frasier! So it didn't matter how I sang along....