That doesn't mean you have to splash the cash, you can buy a full out, get bits and bobs from charity shops or do some DIY. Either way, make sure you put in some effort, and the more of you the merrier!
Check out these fancy dress shops...
Luvyababes (90-92 Albion Street, LS1 6AD)
West Yorkshire Playhouse Costume Hire (6 St. Peter's Square, LS9 8AH)
Dress Up and Party (34 North Lane, LS6 3HE)
Dr. Jekyll's (27-29 Headingley Lane, LS6 1BL)
Otley Run Fancy Dress (12 Aberdeen Grove, LS12 3QY)
Can't afford that? Don't worry. Head to these charity shops and see what you can find...
British Heart Foundation (4 New Market Street, LS1 6DG)
Cancer Research (28 Lands Lane, LS1 6LB)
Oxfam (45-47 Otley Road, LS6 3AB)
Martin House (5 Otley Road, LS6 3AA)
Sue Ryder Vintage (57 Otley Road, LS6 3AB)
And if you're looking to spend next to nothing, there are still plenty of great fancy dress ideas. Time to get creative!
The Simpsons: Everyone in the group can take a character, get the artist in the group to the make masks, and tackle Marge's wig with some cotton wool pads or feather duster.
Mario & Luigi: One of you wears red, the other in green, wear jeans or dungarees, a hat, draw on a moustache and you're sorted! If you're really up for it make a cardboard car too.
Army: If there's enough of you for a troop then this is an easy but effective theme. Pull out any camo, khaki or black clothes you can find then you'll only need body paint and a bandana.
Now you know what to wear, here are 8 reasons you MUST do the Otley Run...