Here are my favorite number segments, from my favorite years of the show, which only cover the numbers 2 through 12:
2:
The 2-2 Train
Grover's lecture on the number 2 (3-part sketch)
Harvey Kneeslapper's "I'd Love 2" prank.
3:
3 song (pennants, butterflies, birthday presents, etc.)
Roller coaster #3 ball film (cherry version)
Donnie Budd's "Three on Lady's Lap"
"I See a 3!"
3 Mice (Swedish Number cartoon, gotta love the 3 in a swiss cheese motif)
4:
Scanimate Count to 4.
"Four Song (Song of Four)"
The Story of "Funny Four"
How many legs does a horse have?
Jazz #4
4 people, 4 wheels, 4 doors, 4 windows create a carpool.
4 dolphins (Swedish number cartoon)
5:
Pinball #5
Spraypainting a 5 on pavement.
A number 5 looks for his lost brother.
Five firefighters battle a flaming 5.
6:
"I'm six years old today!"
"Six Soccer Socks"
Bert sings about six.
The number six displayed in a variety of ways (with pixelation transitions)
7:
Mean Joe Green Coke parody: Have a 7 and Smile!
"Seven Sweet Sopranos"
A man blows seven bubbles.
"As I Was Going to St. Ives"
8:
Moving truck takes away an 8 among a group of numbers ranging from 1 to 12.
The 8 Brothers Circus
8 Bats (Swedish Number cartoon)
Lefty tries to sell Ernie an 8.
"Eight Penny Candy Man"
9:
Arranging and counting nine people. (Live action)
"Dinner for Nine"
"The Old Woman Who Lived in a Nine"
"Bumble Ardy #9"
10:
Jazz #10
"Ten Tiny Turtles on the Telephone"
11:
The blonde Anything Muppet girl who wrires a number 11 on a slate, and demonstrates that it looks the same right side up and upside down.
"Eleven Cheer"
The Ringmaster and his eleven purple pooches.
Pinball #11
12:
Supermarket worker stacks 12 cans.
A mother bird brings a large number 12 to her offspring.