Lobo (Roland Kent Lavoie) scored his first hit in 1971 with "Me & You & a Dog Named Boo", which peaked at #5 on the Hot 100, then hit #1 on the Adult Contemporary chart.
Country singer Stonewall Jackson chose "Boo" for his last single, peaking at #7 later in '71 on the Billboard country chart. The kids from The Brady Bunch recorded their own version, heard on The Brady Kids the next year. I believe Maureen McCormick was on lead vocals for this version. I'll see if I can find it while scoping out episodes for future use on Saturday Morning Archives.