I Choo-Choo-Choose You

 is a recurring task requiring the player to add their first 5 friends on Tapped Out. Other Springfield does not count towards this total. Upon adding a friend, the quest awards a Donut, until the player has a total of 5 friends. Subsequent additions of friends do not earn the player any rewards.

Trivia

 * It is the only task that can be skipped with donuts.
 * Skipping it will not yield the quests' rewards.