The Lollipop Guild was a group of Munchkins in the Munchkin Country, who welcomed Dorothy Gale to Oz with song and dance upon her arrival, in the 1939 movie. Since then they have also appeared and been referenced in other Oz-related sources.
The Wizard of Oz (1939 film)
The members of the Lollipop Guild are all male, and all have huge lollipops. The song they sing to Dorothy goes as follows:
We represent the Lollipop Guild
The Lollipop Guild, the Lollipop Guild.
And in the name of the Lollipop Guild
We wish to welcome you to Munchkin Land
After their song, they retreat into the crowd of Munchkins. ("The Wizard of Oz")
Once Upon a Time
Regina sarcastically references the Lollipop Guild when discussing the Wicked Witch of the West occupying her castle, saying "I don't care if the lollipop guild is protecting her, I can lower that shield on my own." (Once Upon a Time: "Witch Hunt")