The Red version of The Face. Unlike The Face, he has extremely fast attacks, short range and high speed. Shy Boy has 35,000 health at 100% strength magnification and even more when buffed, making him a very annoying enemy in mid-game, so try exploiting his dual-trait weaknesses. When defeated, he drops a good amount of cash.
When choosing a status effect to inflict on Shy Boy, Slow is an excellent choice because Shy Boy's greatest asset is his high movement speed. While Sanzo Cat and Can Can Cat will get the job done, Enchantress Cat will inflict the Slow effect more safely due to better range, and is the best unit to inflict the Slow effect with in this case.
Butterfly Cat will make this enemy much easier as it does massive damage to Floating, just beware of the unit having single-target attacks.
Sometimes when Shy Boy is in attack range and a boss is spawned, he moves so fast that he can end up passing under most shorter-ranged cats. This is because cats sent flying back from a boss shockwave travel backwards at 30 movement speed, and Shy Boy has >30 movement speed.
Inside the game files, Shy Boy is entry #19 while The Face is entry #20. This implies that Shy Boy was originally going to appear before The Face.