Alt text: picture of a Costco mechanical fish (cat) toy taken apart.
I had one of these fail last night from the battery lead coming off as pictured. That is something I expected. Upon opening the mechanism, both sides of the lithium cell have very concerning damage in a piercing type of abrasion. The cell is relatively small.
Speculatively, I expect the stuffed toy is flammable, making this an ideal house fire starter if the cell gets bridged layers in the battery from a puncture and goes into a runaway state.
All it needs is a way to secure the battery with some double sided tape and extra insurance like some kind of soft filler fabric or material to stop it from rattling around. Maybe add a bit of hot glue to the battery leads at the circuit board to insure they do not fail from a lack of strain relief.
I haven't retraced the circuit, but the battery looks fine otherwise. It appears to have a DW01 like protection board at the cell, and a 4054 batman according to the silkscreen.
This is a serious issue that should not be ignored.
I updated the post to reflect the "(cat)" toy nature in the alt text first line. Sorry I took this for granted as a clearly understood context as a common cat toy (in the USA) and failed to describe it as such.
I posted it here because I wanted to reach the most significant audience. Posting this in electrical engineering would have missed the majority of people this is intended to inform.