Meh.cs

public class MyAccount{
  public string UserName{get;set;}
  public Guid Id{get;set;}
  public IEnumerable<MyBullShitClaimEntity> Claims{get;set;}
  public int EPenisSize{get;set;}
}

public class MyUserIdentity : IUserIdentity {
  public string UserName{get;set; }
  public IEnumerable<string> Claims{get;set;}
  public string AwesomenessFactor{get;set;}
  public MyUserIdentity(IUserIdentity userIdentity) {
    UserName = userIdentity.UserName;
    Claims = userIdentity.Claims;
    AwesomenessFactor = "unknown";
  }
  public MyUserIdentity(MyAccount account) {
    Claims = (from claim in account.Claims select claim.Value).ToList();
    UserName = account.UserName;
    AwesomenessFactor = "I am this [" + account.EPenisSize * 10 + "] awesome."
  }
}

public static MyUserIdentity AsMyIdentity(this IUserIdentity useridentity) {
  if (userIdentity == null) return null;
  return useridentity as MyUserIdentity ?? new MyUserIdentity(userIdentity);
}

<div class="metro bootstrap">@Html.CurrentUser.AsMyIdentity().UserName is @Html.CurrentUser.AsMyIdentity().AwesomenessFactor</div>