Unless the cat is VERY cleaver they might not be able to pop out and and by their owner a birthday card so this is the next best option.
A birthday card with cute picture of a cat wearing a birthday hat sat beside a birthday cupcake with a candle. Lower case rounded text above reads Happy Birthday from the cat.
Retail Snapshot
Material: 350gsm card stock | Finish: Matt laminate | Blank inside | Dimensions: 12.6 x 17.8cm (5 x 7inches) | Weight: 18g (0.65oz) | Case Pack: 6 | MOQ: 6 | Made in United Kingdom | Standard UK letter post