Sounding today more like an episode of Midsomer Murders than a title stemming from a classic of children’s literature, the Bears of Little Brains is a reminder that those of us who work in science can all to easily become bears of little brains, falling into our own heffalump traps, and setting ourselves on the trail of a woozle. We may publish something only to find, being a Bear of Very Little Brain, that a Thing which seemed very Thingish inside us is quite different when it gets out into the open, and has other people looking at it. And so it was with the second Walach publication, the research letter about children wearing masks inhaling high concentrations of carbon dioxide, which Dr No mentioned in a comment to his last post. The demolition jobs done on twitter of Walachs et al’s research letter were swift and vitriolic, and the comments tab on the letter itself is turning into an ever lengthening dossier of the delusions held by the letter’s authors. Retraction is increasingly looking inevitable.