Big Bird and Elmo are excited, because they've got a special song for two friends, which they are. They count each other, and sing "One and One Make Two." They almost sing it again, when Abby Cadabby appears in a poof, and asks to join them. Suddenly, Big Bird realizes the song won't work this time, because it's a song for two, and if Abby joins them, they won't be two anymore, but three. What to do? Abby suggests making herself disappear, but that turns out to be not such a good idea. The three friends decide they should ask Gabi what they should do. They explain their predicament, and Gabi suggests they sing a song for three instead of two. What a great idea!
