fantasy_football_league.rb

class FantasyFootballLeague < ActiveRecord::Base
  has_many :memberships, :as => :app
end

march_madness_bracket.rb

class MarchMadnessBracket < ActiveRecord::Base
  has_many :memberships, :as => :app
end

membership.rb

class Membership < ActiveRecord::Base
  belongs_to :app, :polymorphic => true
end

user.rb

class User < ActiveRecord::Base
  has_many :memberships

  #
  # We want
  #
  has_many :march_madness_brackets, :through => :memberhsips
  has_many :fantasy_football_leagues, :through => :memberships
  #
  # But the above code does not work >(
  #

end