It's a play on the phonetic pronunciation of Happy Birthday, popularly used in Latinx/Hispanic cultures. Sapo is slang for frog, and verde is the word for green.
(Think the Happy Birthdaysong) Sapo verde to you, sapo verde to you, sapo verde INSERT NAME, sapo verde to you!
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.