Establishing the PPPoE connection with controller there are few characters example '!', '@', '%', '^', '&', '*' working fine with these however '#' is also very common used characters which will be supported from 6.3.0.1 or 6.1.3.10 AOS before that it is not support.
Below is the test result from 6.1.3.10 AOS
(Aruba3600) #show ip pppoe-info
PPPoE username: #0001@t-online.de
PPPoE password: <HIDDEN>
PPPoE service name: <NONE>
PPPoE VLAN: 2
PPPoE is UP
Server IP: 10.0.0.1
Gateway IP: 10.0.0.1
Primary DNS: <NONE> Secondary DNS: <NONE>
(Aruba3600) #show version
Aruba Operating System Software.
ArubaOS (MODEL: Aruba3600), Version 6.1.3.10
Website: http://www.arubanetworks.com
Copyright (coffee) 2002-2013, Aruba Networks, Inc.