Axolotls and frog print on the bLen pen series by Zebra Japan — these designs are part of a collaboration limited release with Japanese stationery brand Green Flash. The bLen pen is described by the company as a "stress free" writing experience for its smooth and vibration free features.
My daughter tested these pens and commented: "It feels kind of scratchy on paper but I really like it because of the axolotl." Honest reviews from children — only at Paper Treats! 😉