Al gets a new remote for his TV and uses it right away without any coding. This indicates that the remote was made specifically for his model TV. So how is it controlling Marcy's? Even if it was a programmable remote, Al would've had to enter codes for both his TV and Marcy's (it's possible that he got it coded for his own TV wherever he bought it, assuming he knew the model number of his TV, but the store wouldn't be able to code it for Marcy's TV as well), and even if he did, he would have to switch the remote between controlling Marcy's TV and his own (that's assuming it accepts two TV codes in the first place), and we only see him hitting the "channel" buttons. Long story short, unless they had the exact same model TV (unlikely), Al's new remote couldn't control Marcy's TV and his own at the same time. Not to mention that when Al tries to control Marcy's TV, he is holding the remote out his door and across the street - it would never reach her TV.