April 25, 1951: As a kid, this is what I thought golf was

The first use that I've noticed in Peanuts of thick, outlined letters, here in a word balloon.

Notice that Charlie Brown's shirt is missing its stripe in the second panel, probably because it wouldn't read well with his arms and club in the way.

April 21, 1951: Frieda would love this

Good poses for Snoopy here. Shermy's apology to an annoyed Snoopy is a nice touch.

April 20, 1951: Team sponsorship

The mud pie strips have been leading up to this, which wouldn't have been as funny without them. It's not the last one, though.

But this strip is notable because it's the first in which Charlie Brown plays baseball!

April 19, 1951: A dog without gravity

Later on, Snoopy would lose his ability to experience, or express, this kind of enthusiasm, although he'd pick up other means. But we do get another three-quarter perspective leap out of him while he's still capable of it.

April 17, 1951: The bird's a solo act

No thought balloons yet, but Snoopy's dealings with a decidedly non-Woodstock bird are looking more human.  Something to notice: when Snoopy's head is facing the "camera" in three-quarters perspective, his eyes are a little closer together than in previous strips. Earlier he looked almost fish-eyed, but they've begun to migrate to the front.  Over time, all the characters' eyes would move closer together, which helped to give them a more mature appearance as the situations became more complex.

April 16, 1951: Snoopy chases bird down stairs

That bird is back, and so is the scribble of ire.

Eventually, it's either this bird or one that looks a lot like it that builds a nest on Snoopy's stomach while he lies atop his birdhouse EDIT: dammit doghouse, and it's one of the birds to be born from that nest who would become Woodstock.

Woodstock would pine, around Mother's Day every year, for his mother. Schulz and Peanuts: A Biography notes that Charles Schulz's mother was rather cruelly taken from him within a week of his going overseas to fight in World War II (her funeral was the day before he shipped out), a blow it seems he never recovered from.

But anyway, it's weird to think that the unobtainable love and affection that Woodstock sought from his absent mother all those years may be right here, in this very bird.

April 14, 1951: Scenes from a world without spellcheckers

Another Catch-22 joke, another version of the finding-flashlight-in-dark-attic bit from earlier, this time involving the difficulty of using a dictionary to confirm spelling.

April 13, 1951: She's right

Welcome back to Violet's mud pie corner. When life hands you dirt, you make dirt-ade.

April 12, 1951: More shirt stuff

More playing around with Charlie Brown's shirt. I like how it's Snoopy who's offended by Patty's confusion.

April 11, 1951: "This is an exclusive number!"

Charles Schulz must have come up with Charlie Brown's "Crayola shirt," as I call it, as a way to make the character visually distinct from the others.  It would not be overstating things to say that it is known the world over.

Snoopy edges still closer to humanity here.  Notice that he has no thought balloons in these early strips.  I might be wrong here, but I seem to remember that Peanuts was the first strip that used them to present a way for unspeaking animals to kinda-sorta talk.