* GoddamnedBats: The AI companies, town councils, and those [=UFOs=] that appear and attack your (and ''only your'') trains and buses.
* GoodBadBugs: A lot of them were also fixed by ''[=TTDPatch=]'' and ''[=OpenTTD=]'':
** In the initial UK release of the original game (and earlier demos), building a long enough tunnel would cause [[WritersCannotDoMath the cost]] [[PowersOfTwoMinusOne to run negative]], and you would make over a million dollars/pounds/whatever. Bad in that if you earned enough money, your cash would flip into the negative, and you would suddenly be millions in debt. Fixed in the US release and ''Deluxe''.
*** Another overflow bug fixed in ''Deluxe'' was that a boat or a plane could make enough money from a single trip that the payout would flip over and result in the vehicle losing money.
** In the original, with level crossings, whoever owned the railway owned the square. This meant that you could screw over AI road construction by laying rails over their roads and destroying the road. Fixed in ''Deluxe''.
*** Those same level crossings could be traveled over by trains of any company, which allows you to trap a rival's train or even make two companies' trains crash into each other if they have properly aligned stations. That wasn't fixed in ''Deluxe''.
*** If you lead a train to a level crossing and reverse it at ''just'' the right time, the crossing will close indefinitely. Useful to trap a rival's trucks. Also wasn't fixed in ''Deluxe''.
** The original game included two minor glitches in the way it worked out signaling. A railway depot counted as a normal piece of track for signals, and the signaling algorithms didn't distinguish between the tracks of different companies. On their own, these bugs had no real effect. Together, however, you could build a loop of track between the end of a rival's railway station and the nearest train depot. Any train that entered the station would then trigger its own signals, and it would ''never be able to escape the station''.
** The oil rigs, which usually accept passengers and mail, can be screwy in the cargoes they'll accept. Some times they won't accept anything, other times they'll accept odd cargoes such as wood and oil!
** Towns in the "Tropical" climate usually only have banks which accept diamonds but don't produce them, but sometimes a "Temperate" bank (which accepts ''and'' produces diamonds) will be built if the town has over 1,200 population, even if the town already has a "Tropical" bank. Oddly enough, this doesn't seem to affect the "Arctic" climate, which uses the same non-producing banks, albeit with gold instead of diamonds.
** In the original game, by judicious building and bulldozing of stations of different types, you can spread the station's reach to ridiculous levels. ''Deluxe'' nerfed it by limiting the spread to seven tiles from the station's sign, but ''[=OpenTTD=]'' allows the adjustment of that limit and to join new stations to existing ones easily by pressing Ctrl while building and choosing a station from the list that pops up.
** If you have a competitor's info box open when their company goes bankrupt, you'll see that their company value will rise to a ridiculous amount. If you invested 75% in that company previously, selling off the shares will net you a lot of money. However, there's a very good chance the game will just crash when that happens.
** The game will sometimes offer multiple subsidies for the same service. While the payout isn't multiplied accordingly, the multiplied subsidies effectively extend their longevity past the usual single year.
* MemeticMutation : "Yate Haugan" and "Guru Galaxy", the [[LawyerFriendlyCameo lawyer-friendly]], post-Original renames of the Concorde and the Lockheed Tristar.
* StopHavingFunGuys: It's a Chris Sawyer game. He has issues with people modding the game to make it more of a sandbox.
* ThatOneLevel: The "Toyland" climate doesn't have a very good reputation with fans due to its [[TastesLikeDiabetes overbearing cuteness]] at the expense of realism and having the worst selection of vehicles, especially for trains and aircraft.