Cloud Gags
Starting with Season 20, the show got a new intro sequence, and with it, the producers added many new gags to go along with the usual Blackboards and Couch Gags. One of these new gags are various cameos and gags within the very first scene in the intro as the title of show appears in the clouds. Here's a list:

Sherry Bobbins flies by from the left with her umbrella.
LABF15 - Bart Gets a Z
LABF18 - Pranks and Greens
A Stork flies from the right, carrying Maggie.
LABF16 - The Great Wife Hope
LABF19 - Rednecks and Broomsticks
Homer floats from the right drinking a beer in a chair that's floating by balloons.
LABF17 - The Devil Wears Nada
MABF01 - O Brother, Where Bart thou?
Ralph flies by from the right hanging onto a kite.
LABF20 - Once Upon a time in Springfield
MABF10 - The Greatest Story Ever D'ohed
Agnes Skinner somehow rides her bike from the right.
MABF02 - Thursdays with Abie
MABF06 - The Colour Yellow
Plopper swings webs from the left.
MABF03 - Million Dollar Maybe
The family ride Chitty Chitty Bang Bang from the left. Homer honks the horn.
MABF05 - Boy Meets Curl
Radioactive Man and Fallout Boy fly in from the right.
MABF07 - Stealing First Base
Captain Lance Murdock flies in from the right on his bike, screaming "Yee-Haw!"
MABF08 - American History X-Cellent
Kang and Kodos fly by from the left in their spaceship.
MABF09 - Chief of Hearts
Krusty trapezes from the right and is caught by Sideshow Mel on the left.
MABF11 - The Bob Next Door
The Bumblebee Man flies in from the right.
MABF13 - Moe Letter Blues
The FOX Satellite flies by from the left as bits break off.
MABF14 -The Squirt and the Whale
Flanders, as an angel, flies in from the bottom of the screen.
MABF15 - Judge Me Tender
Mr. Burns flies a giant blimp with his face on the side.
MABF17 - Loan-a Lisa
The three eyed crow flies by from the left with a Rat in it's mouth.
MABF18 - MoneyBART
MABF19 - Donnie Fatso
Otto flies by in the School Bus
MABF21 - Elementary School Musical
The three eyed crow flies from the right carrying Blinky in it's mouth.
NABF01 - The Fool Monty
The FOX copter flies in claiming that it's not suitable for anyone under 75.
NABF02 - How Munched is that Birdie in the Window?
Martin is hung from a flagpole in a wedgie as the three eyed crow flies by from the right.
NABF03 - Moms I'd Like to Forget
Mr. Burns is flying an old fashioned plane, while Smithers hangs onto the tail.
NABF04 - Flaming Moe
Moe flies by on a pair of skis, he gets hit by the I in "Simpsons"
NABF05 - Homer the Father
Homer, dressed as Pie Man and Bart, dresses as The Cupcake Kid fly by from the right.
NABF06 - The Blue and The Grey
Santa's Little Helper jumps up to catch a frisbee in his mouth.
NABF07 - Angry Dad: The Movie
Santa's Little Helper is ridding his doghouse in the sky and gets shot at.
NABF08 - The Scorpions Tale
Professor Frink flies by with a Jetpack.
NABF09 - A Midsummers Nice Dream
The Futurama theme plays as the Planet Express ship flies by.
NABF10 - Love is Many A Strangled Thing
Maggie is riding on a paper airplane.
NABF12 - The Real Housewives of Fat Tony
Homer is flying on a magic carpet.
NABF13 - Homer Scissorhands
Hank Scorpio flies in his jet claiming that it was either that or a Porche.
NABF14 - 500 Keys
Princess Penelope swings by in her "unicorn"
NABF15 - The Nedliest Catch
Otto slides down a rainbow.
NABF16 - The Falcon and the D'ohman
Arnie Pie falls out of his helicoper shouting "The Simpsons, wha?"
NABF17 - Bart Stops to Smell the Roosevelts
Kang (or Kodos) fly by in Santa's Sleigh.
NABF18 - Holidays of Future Passed
Groundskeeper Willie uses his Leaf Blower to fly around.
NABF21 - Replaceable You
Krusty and Sideshow Mel trapeze through the sky. Sideshow Mel jumps off but Krusty misses in grabing him.
PABF01 - The Man in the Blue Flannel Pants
Bumblebee Man is being chased by a swarm of bees.
PABF02 - The Ten Per-Cent Solution
Maggie is wearing a parachute and Grampa is wearing a harness. Maggie's sash says 2012, while Grampa's says 2011. Maggie is lowering, while Grampa rises.
PABF03 - Polically Inept, with Homer Simpson
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