I noticed this watching a different DVD - It's the Great Pumpkin, Charlie Brown.
I mistakenly thought Andy from Come Back, Shame was Christopher Shea, who voiced Linus in the early Peanuts specials. He would've been around the right age and the voice sounded the same. And according to his bio, he was in Shane, which Batman was spoofing.
But apparently I was wrong.
Andy was played by brother Eric Shea, who was two years younger. And according to credits, Andy would also voice Linus after his brother.
I think I got all that right.
I also didn't realize Christopher Shea passed away ten years ago.