Alan's only an occasional Merry Man showing up late in the legend. Still he is popular, sometimes as the narrator of the stories. His name is spelled a variety of ways -- Alan, Allen, Allan and Allin. (My own name is Allen, and so I know just how many ways there are to spell or misspell this name.)
Robin came across a happy man in scarlet clothing. Amazingly Robin didn't start a fight. But the next day, he saw the same man depressed and unhappy. He stopped the man to ask what was wrong.
Alan was to marry his true love that very day. But instead, she was given to an old, cruel, rich knight. The young man said he'd be Robin's servant if the outlaw could save his true love. Disguising himself as a bold harper, Robin snuck into the ceremony. He blew on his horn and summoned the other Merry Men, with Alan a Dale in the lead. They stopped the wedding, crossing the knight and the bishop. Then, Little John put on the bishop's clothes and married Alan and his true love. Other versions have Tuck performing the wedding service, which would certainly make it more official.
Click here to read the ballad Robin Hood and Allen-a-Dale.
Alan's wife has been given different names, although Ellen seems to be the most common.
There's an early reference to this tale where it's Will Scarlet's bride who is rescued. Since both Will and Alan dress in scarlet, they can be confused. And somtimes both are musicians.
Usually, Alan doesn't serve the Merry Men as a fighter. Instead he is a minstrel, providing musical entertainment for the outlaw feasts. Alan also spins tales of Robin's deeds, spreading the bold outlaw's fame throughout the land. In most tales, Alan is a master musician. But in one television show, he's hopelessly tone deaf.