I guess this is kinda a duh but... Jupyter queues messages with ZMQ so that if pack up my laptop and go somewhere else while executing, the messages get delivered once there is internet again? Seems like that just happened. Delightful!
It wasn't mine either, previously. Esp with Iopub rate errors and stuff I didn't expect it. I didn't *refresh* though. I just opened went back to the page. Maybe refresh does a purge from time t < now()? I'll try to replicate on my way home.