The Mechanics of a remote control - on or off 
Copy or sample.
The laziest way to copy a remote control is to sample the data from the original. You store the data like an audio recording rather than note down the words someone is saying.
There are downsides to doing it this way.
- It consumes far more memory.
- It doesn't deal with the issue of when a button on the remote is held down.
- The button response on the copy is poor.
The chips in a remote control are very limited in storage capacity. RAM is often no more than 80 bytes and data storage is 2000 bytes. Considering that a mobile phone or PC may have 128000000000 bytes it is not a lot. More memory is a lot more money and quite honestly a waste.
To copy a remote one must decode the data from the original remote control, not just record it, if you want it to work well.
Sample Quality
A remote sample will not be particularly accurate. Usually good enough, sufficient to work most of the time. Some companies offer remotes that allow customers to copy data themselves. They record the data and the remote replays it.
The sample would be a simple series of on/off lenghts, something like this:
350,20,59,19,60,20,19,21 ...
A decoded sample would send a much more accurate set:
352,20,60,20,60,20,20,20 ...
To analyse and sort the numbers properly takes human effort or computer power.
Each press. Toggle or repeats.
The remote controls that use the bit shift encoding will send a part of it as 0_1 the first time you press a button and then 1_0 the next. This way the TV knows you have released the button and pressed again. If your cat walks in front of the TV, it doesn't matter, the signal is the same until you let go and press again.
Where this type of encoding is used (NEC) they usually send the first 2 parts again repeatedly until the button is released.
If you were to sample the remote there will be many issues with replicating this. Hence why remotes that use that method only "just about work".
Dual touch
Our remote controls and many others have a dual touch system. This is usually reserved for a small number of functions.
The eject is the most common use for this. If you hold the stop button down for a couple of seconds the eject code is sent. Anything less than two seconds and the stop is commanded
On the subject of eject, one of the biggest foibles of mankind emerges. To take a disc out and change it, one assumes you have to get up and go over to the DVD/CD player? Or do people spend years training a dog t o get it out. If people can't eject the disc using the remote; emails are sent, messages are delivered and phone calls are made right way. (Always before reading any supplied keymap or looking for the eject symbol.) Pr essing the eject on the DVD itself won't do - it must be done on the remote. Maybe people just like opening and closing the draw over and over from the comfort of their sofa. Who knows.
Eggs and mischievous data
In computer games people have discovered a few secret 'eggs', elements in a game that are not advertised. It may be a cave that is hidden or a special tool that can be found if you search very hard.
You can store data using a variable and name it something like 'shoppingList'. This is used by the program, but is not visible to the people using it. The 'shopingList' can be named anything - maybe a swear word or something else. Nobody is going to see it unless they take a look at the source code.
The data sent from a remote control is not decoded by the general public very often. What messages can be sent using just the letters 0123456789ABCDEF? However, 65 represents 'a' in ASCII computer code, so lots o f opportunity.
Most boringly we have not spotted much. A lot of manufacturers can choose between 65000+ header values, but way too many select 00FF. You may find that many a DVD remote, especially the cheaper ones, will work so mething else on another device. The play button might bring up the EPG on a Freeview box for example.
You can send a set of commands that unblocks the region code for DVD playback. Certain service menus will appear when codes not on the original are tried on some TVs. You can try sending each number from 0 to 255 and see. However, some will not implement the standard error checking format. People that are keen to uncover such things may have to disasemble the firmware in the TV to locate hidden options.