rathole
Workplace term for unproductive tangential discussion
A topic of conversation that has diverted wildly from the original conversational thread and is generally viewed by all (but the one leading the topic) as being without resolution, or at the very least is uninteresting to others in the group. Ratholes usually open up when related but tangential topics are discussed which are explored in much more detail than is required for the relational reference to the original thread.
I was trying to keep things on topic, but you've opened up a big rathole with all this talk of comic book plot twists.