I added the custom text fields First Name and Last Name to the User account - /admin/config/people/manage. 

Next I created a Rule that sends an email. In the email I use replacement patterns for First and Last name.  When the email is sent instead of displaying the First and Last name it just says "Array Array".  Recent log messages include this notice - Notice: Array to string conversion in RulesTokenEvaluator->evaluate() (line 224 of .../modules/rules/modules/system.eval.inc). Am I doing something wrong or is this a bug?