Sew or hot glue several sheets of felt together to create the fish tails. Use light blue felt with purple felt fins for Alberto and bright green felt with blue felt fins for Luca. Turn right side out and stuff with stuffing and sew (or hot glue) closed. Attach to the back of the bottoms using two safety pins.
For the hats:
Cut fish scale shapes from cobalt and purple felt. Attach to cozy hats using adhesive sheets.
Attach arm fins to the pajama top using adhesive sheets.
Cut feet shapes from sheets of craft foam and cover with felt using hot glue.