Question

Who shows up to get perch and his mother in the middle of the night

Answer 1

Hi, there!
If you mean Percy then it would've been Grover who was his best friend! He's pretty much a Satyr - which basically means he has goat like similarities! If I'm not mistaken it does say he's a goat below the waist and he does have horns!
Good luck, rockstar! Have a great day!