Thumbs UP! by Pentagon is a very bright and colorful album created to bring people happiness and positive energy. The title song “Naughty Boy” is full of mischievous, fun, and humorous parts. The name of the title song in Korean “청개구리” literally means “green frog,” and is also used to describe a person who does everything in the opposite way. The message is to find harmony in mismatch and enjoy each day without worries.
To represent the harmonious mismatch of the songs, the album cover and a sleeve have completely different illustration styles. The front cover is a colorful illustration of the lotus leaves, while the sleeve is full of playful frog footprints. The green frog is not actually shown anywhere in the album design, but its presence is noticeable everywhere.