Charlie Brown appears all over the place!
1) As you enter the island, he is cavorting on the sidewalk in front of the Van Pelt home. He has gotten his first invitation ever to a Halloween Party.
2) He is later found in his backyard, which are the two scenes left of Main Street.
(you cannot go there until you have gotten a pumpkin for Lucy, a bag for Pigpen, and a lemon sucker for Linus)
3) After Linus goes to the mailbox, Charlie Brown and Lucy are playing with the football in his yard.
4) Charlie Brown is at the Halloween Party, and goes trick-or-treating.
5) After the island ends, he is in his yard again, despairing that all he got from trick or treat was rocks.
The name of the island is Great Pumpkin Island. See the related question below.
'It's the Great Pumpkin, Charlie Brown' debuted in 1966.
Charlie Brown awaits the arrival of 'The Great Pumpkin' .
Snoopy
The Great Pumpkin?! that's from charlie brown.
No.
Charlie Brown is on the sidewalk when you enter Great Pumpkin Island, but he spends much of the game in his back yard left of Main Street. Snoopy is at his dog house at the far left of the island. Your first task is in the pumpkin patch to the far right. You have to weigh the pumpkins, roll one back to Lucy's house, give Pigpen the bag, and give Linus the lemon sucker. Then you can go left where Charlie Brown is collecting the leaves with Snoopy.
linus
Rocks
To get to Charlie Brown's backyard, go left past the Flying Ace cafe. You need to complete the pumpkin patch first, then get the pen and invitation, before you can do the Snoopy and Charlie Brown scenes. (see related question)
You are drawing on his head -- the pumpkin gets carved the same way. Whatever face you draw will work.
After Linus mails his letter, go left to where Lucy and Charlie Brown have the football.