Bryan

 Bryan is a unseen character in the second season. He's only mentioned in the seventh episode of second season. Bryan was Jaime Lannister's squire on the day of Willem Frey's wedding tournament.

Backgrund
He's a squire.

Season 2
In the Stark's stockade, Ser Alton and Jaime Lannister talking about Willem Frey's wedding. Ser Alton mentioned he filled in as Jaime's squire, when Bryan threw up on his horse. Jaime said it was Tyrion who made him so drunk.

In the books
In the Song of Ice and Fire novels, there is no character named Bryan.