One of the things WB tried to do was develop some animated series of their own to counterprogram Fox's The Simpsons & King of the Hill. However, despite bringing in two former producers from the former, the network ended up laying an egg.
Mission Hill lasted just 1 season (1999-2000), and not even a rerun cycle on [adult swim] could revive viewer interest, in contrast to [as] reviving interest in Fox's Futurama & Family Guy, the latter of which is still on the air today.
Perhaps the biggest reason why Mission failed was because it was airing on the same night as the Fox toons. Scheduling it on another night might've at least extended its lifespan, but we'll never know for sure.
I never saw the show, so there won't be a rating. Instead, this sample is a public service.