Aid the planet, but when I went back they wanted me to search for missing ships. ( I know bug ) the best part is it used the same model of the aliens from the aid the planet mission. ( never finished that mission. )
My personal favorite ... I beam down and my science officer informs me that I need to scan these carnivorous plants. After a bit of head scratching and scanning I finally realize why I can't find them. The engine threw in the model of giant stone columns for the plants. So I named them "Parthenon Plants".
My favourite screwy ones are when they throw in the Borg into a mission that was clearly not written for them.
"Captain, we've been asked to investigate raids on civilian ships by rebels. We've discovered that the Borg have been arming the rebels..."
Borg giving arms to rebels? Puh-leeze.
"Captain we've been getting reports of pirate raids on transports by Borg. These Borg are renegades and the Borg government have denied all involvement."
Borg Government? Puh-leeze.
"Captain, we've arrived at the empty base, but a Borg ship just appeared. I'll try to warn them away but they aren't responding to hails."
Warning the Borg away? Puh-leeze.
Oh, and my favourite:
"Apparently the Borg were trying to influence the development of the culture to align them with their culture. But their horse lost the race."
The Borg don't influence pre-warp cultures from hidden bases. They assimilate stuff.