And their secret is deciphered- heh heh! So it turns out, in the Tankbot software on iPhone (and presumably on Android), you are prompted to enter the product code from the package. Our Toys R Us non-battling tankbots had codes 1044 for Blue and 1043 for Green. Interestingly, the Brookstone codes are 1880 for Blue and 1870 for Red. Try putting those in the software- voila - a Fire button appears! Another difference of unknown significance, the ToysRUs Tankbots are both stamped 12AB11 on the bottom, whereas both Brookstones are 11AB11. Probably a date of manufacture code, it is also stamped into the respective packages.
Even more interesting- we can drive both Blues simultaneously- there appears to be no difference in the control codes- but the Fire button command is only noticed by the Brookstone Blue. It makes shooting noises and swings side to side for a couple of seconds. Most interestingly, the ToysRUs Blue also reacts to being shot! It moves forward/backward several times and is disabled from commands for several seconds.This was also true for the Green ToysRUs Tankbot (even in its semi-destructed state).