Data corruption happens when the game finds unused bytes in a savegame. Although TFTD is nearly a clone of UFO Enemy Unknown, the byte offsets in the savegames are often different, so weird things happen when files are placed in the wrong game.
Here are a few tricks.
Base on land/water
This function still isn't researched very much. In UFO, get an Avenger (not sure if it was Avenger, surely not Skyranger or Interceptor) then copy CRAFT.DAT and LOC.DAT to TFTD. Then you can end up having 2 ships named ammunition-1 and ammunition-2, nicknamed Transformers. These will have 255 coelacanth tanks and other things. The most interesting thing is that these ships will disappear once an UFO is nearby and turn into those UFOs. For example, a Survey Ship passes nearby your base. Your ammunition-1 will disappear and the UFO will be yours. However, the game will crash once you click on it, since it isn't assigned to any base. It may be possible to control alien ships, but it still is unknown how.
Unused Aliens or Items
It appears that when RESEARCH.DAT is copied from game to game, weird things can happen. There were reports of seeing research items like this unknown weapon or getting a Tentaculat Commander. This function, however, is not completely researched.
Currently we know the aliens are possible to control permanently all this thanks to Quantifier. By those permanent control tests it is assumed that Glitch ranks are useful for reaction and other benefits. as for alien control ship this is impossible since the alien ships lacks a lot of data in TFTD in UFO Enemy Unknown though it is actually assumed its possible to control a Battleship to an extent. this was told in a topic where someone made move one around. as for Glitch Craft Weapons the only one researched has no effect on its enemy and has a very short range.