Game locks up if active worm dies while executing a Fire Punch
From Worms Knowledge Base
If, while executing a Fire Punch, the worm falls into the water and dies, the game will softlock at the "{WORMNAME} IS AN EX-WORM" message. Moving the mouse still allows you to look at the map, and the water continues to animate as normal, but the game cannot proceed.
As this bug will only occur in WormsDC under very specific circumstances, it is unlikely to be encountered in typical play.
Recreating this glitch
In order to recreate it, the following requirements must be met:
Possible Causes
The most likely explanation is that WormsDC is waiting for the attacking worm to come to rest, but as it never does so the turn cannot technically be brought to an end and the game cannot continue.
This bug does not occur in the original Worms. The key difference seems to be that the Fire Punch in WormsDC causes injury to a Worm if you're standing on their head and use the Fire Punch, while the original Worms does not.
Testing oddities
During testing in emulation, the emulated Amiga 1200 would also lock-up at Workbench temporarily during start-up after this glitch had been performed. Additionally when this bug was first discovered, reloading WormsDC would cause the game to crash during loading as it would if booted on an Amiga CD32. However, this has not occurred during follow-up testing.