My mama grew up watching Scooby-Doo when she was a kid, then I grew watching this cartoon as a kid. I also watched the 2002, 2004, 2009, and 2010 film versions of the franchise, but when I heard that a reboot is in the works, I thought a fancast should work. This is who should be cast in this reboot.
Fred "Freddy" Jones: Chris Zylka
Fred is known for often taking the lead in almost every spooky mystery to solve, often pairing up with Daphne to do so. Despite appearing to be a gentleman, he can be bossy at all times, especially in forcing Shaggy and Scooby into jumping along. Chris Zylka, known for his roles in Shark Night and Piranha 3D, has the acting chops and look for the role, and with a blond haircut and facial shape similar to Fred's, Chris, as an emerging actor, will see the role as his breakthrough one.
Daphne Blake: Holland Roden
Daphne comes from a very wealthy family, and is nicknamed "Danger Prone Daphne" , due to her knack of getting into danger. Holland's Teen Wolf character, Lydia Martin, is a popular high school girl and a banshee, so she will be so divine playing Daphne.
Velma Dinkley: Alexandra Daddario
Velma is an intelligent young girl known for her love of science. She is usually seen as the one to figure out the doing mystery besides Fred. She is also mainly the one giving Scooby a Scooby snack, loses her eyeglasses everyone a villain starts chasing after her, and her catchphrase it's "Jinkies!" I know this is an unlikely choice for Velma because Alexandra plays so many dramatic roles, but she has the Velma look, and is good at solving mysteries as Annabeth Chase, so I can't to see her jumping on the comedic side of acting with this role.
Norville "Shaggy" Rogers: Dave Franco
Shaggy is the somewhat gooftroop of Mystery Incorporated. He often uses hedge words, such as "Like" and his catchphrase is "Zoinks!" The main owner of Scooby-Doo, they easily get and run away from each other, and eat unusual food combinations together, solve mysteries together (sometimes with the guidance of Velma Dinkley). James Franco's little brother is learning to do comedy under his shadow, and this role... is definitely open for him.
Scooby-Doo: Frank Welker
Frank Welker is Scooby-Doo, and nobody can do the role like him.