In most images of the Annunciation the three main protagonists are the Archangel Gabriel, the Virgin Mary and the Holy Spirit (taking the form of a dove). Very, very occasionally, the dove will be accompanied, or even replaced, by a tiny figure (who often carries a Cross).
We can see such a figure in a beautiful medieval painting of the Lignum Vitae (Tree of Life), which hangs in the Galleria dell' Accademia. It was painted, circa 1310-15, by Pacino di Bonaguida for the Convent of Monticelli in Florence.
The large wooden panel depicts a tree-shaped cross, which symbolises the Tree of Life. The scenes in the roundels hanging from its branches represents episodes from Christ's life. One of the roundels contains an image of the Annunciation, in which it is possible to discern a tiny figure heading towards the Virgin Mary.
More than two centuries later, the Council of Trent (1545-63) would discourage such representations, as they could lead people to think that Christ was fully-formed before entering Mary's womb, thus making the Mother of God a mere passive receptacle, rather than an active participant, in the Incarnation.