I've been working my way through NADDPOD, and there was a great session where
NADDPOD
the party is in an airship being chased by Knights of Hell riding Nightmares. Axford polymorphed the Duke of Hell's steed into a dolphin and they fall out of the sky.
The GM is laughing, but musing that this was supposed to be a big fight and Emily just dinked it.
Another player comforts him with, you forgot wizards are bullshit.
It was such a great session. It really emblemizes how I try to approach being a GM. Have a prepared roadmap, but have space around the road for the characters to take a roadrally off-road.