After that, they hit again with "Wake Up, Little Susie."
And then they hit again with "All I Have to Do is Dream."
Three gold records in your first year ain't bad. Even their other release that year, which didn't go gold, was a fine two-sided hit. Here's one side:
They went on to become the most popular duo in chart history, with Don singing the low harmony parts almost exclusively and also singing most of the solo lines. According to the Wikipedia entry, they had 35 Top 100 singles in the Billboard charts, 26 of which reached the Top 40. They eventually had an acrimonious split and went on to solo careers, reuniting in the 1980s for some very nice albums, my favorite of which is Born Yesterday.