Clokr_ is wrong then. 100% it's a hack. He showed me, and I also saved a replay of some other things he did. We traded information.
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He's using a mac, and claims to have modified the "buttons".
He also said he can turn a nydus canal exit into a drone/mutalisk so that you can move the exit anywhere and it will work. He can make any worker turn into any building, and can even spawn vespene geysers out of nowhere. There are probably other things he can do, but whatever.
Hacks
do save in replays. Hacks that WORK ONLINE save in replays, and command hacks especially work in replays.
QUOTE
They modified the probe's build range so that the buildings warped in anywhere (building anywhere on the map without moving).
This is a different and very easy hack to make, but requires some knowledge about Starcraft commands(orders.dat). (I can show you this myself)
Replays are just simulations of the actual game, which records all actions done by players and saves it so that it can be played back. A modification CAN NOT be saved as a replay, like say I made a mod that gave SCVs 70000 HP and saved a replay. If you view the replay in normal starcraft, the SCVs will have their 50 hp, or whatever their normal hp amount is.
There is no possible way corrupted replays can cause a person to morph his drones into mutalisks.
This bug could have also originally been done in the 1.04(or before?) patch without the use of hacks.