Artist's commentary
Tick-Tock
Valentine's return gift from Mephistopheles.
Tick-Tock, Chaldea's mascot.
This was Mephistopheles's grand scheme to take the mantle of the mascot away from Fou.
Unfortunately, it's not as popular because it explodes whenever it is jostled.
That seems strange to both Mephistopheles and Nursery Rhyme.