The beauty of cartoon characters is that they never have to age. Tom has been chasing Jerry for nearly eight decades — or roughly 325 "cat years" in Tom terms. Bart Simpson has been in fourth grade since 1987.

While toons never get older, they certainly undergo changes. Animation techniques and technology change. The cartoonists themselves come and go. Properties change studios. Each era has its own distinct aesthetic.

Some of these beloved characters have gone from cinematic shorts to Saturday morning cartoons to streaming on smartphones. Let's take a look at just how much our favorites evolved over time. We juxtaposed one image from the character's debut with the most recent iteration. The new looks might surprise you — as well as the originals.

Scooby Doo

Image: Warner Bros.

The Mystery Mobile first rolled onto screens in September 1969 with the premiere of Scooby-Doo, Where Are You! The Hanna-Barbera characters have been a constant presence for the last half century, appearing in movies, on merchandise, in video games, etc. The latest take on Scooby, Shaggy and the gang is called Be Cool, Scooby-Doo!, which currently airs on Warner Bros.' Boomerang network and streaming service. It's a distinctly different look, one that is far more stylized. Shaggy's goatee seems to have grown into a beard, too.

Tom

Image: MGM / Warner Bros. Television Distribution

The feline had a fuzzier look in his debut, "Puss Gets the Boot," which was released to theaters in February 1940. This realistic depiction morphed into the more cartoony look. He seems to have lost his claws, though his eyes remained yellow.

Jerry

Image: MGM / Warner Bros. Television Distribution

Of course, we can't mention Tom without his nemesis, Jerry. The mouse got a little rounder, a little cuter. The modern version is not too different.

Bugs Bunny

Image: Warner Bros.

Also making his official debut in 1940, Bugs Bunny popped out of his hole in "A Wild Hare" with a scrawnier, more sinister look. Today, Bugs has a bolder, more minimalist look in his current series, wabbit., which revives many beloved Looney Tunes characters on Boomerang. Including…

Porky Pig

Image: Warner Bros.

This is a case where old and new might look drastically unfamiliar to folks. Porky predates Bugs, as he made his debut in "I Haven't Got a Hat" in 1935. His stutter has never changed, at least.

Wacky Races

Image: Warner Bros.

This year, Boomerang has rebooted another Hanna-Barbera favorite, Wacky Races. The original premiered as a Saturday morning cartoon in 1968, and spawned two spin-offs the following year in The Perils of Penelope Pitstop and Dastardly and Muttley in Their Flying Machines. Dick Dastardyly and his giggling dog Muttley remain the focus of the new show. His purple Mean Machine looks to be a similar model.

Snoopy

Image: Warner Bros. / 20th Century Fox

Peanuts made its debut in newspapers in 1950, but it was not until A Charlie Brown Christmas in December 1965 that we saw Snoopy come to life. The pup has a refreshingly retro look in the most recent TV special, 2011's Happiness Is a Warm Blanket, Charlie Brown. The Peanuts Movie in 2015 gave him a textured "3D-2D" appearance which stayed true to the original form.

Garfield

Image: CBS / Mediatoon Distribution

Jim Davis' lasagna-loving cat changed significantly in the pages of his daily comic strip, so it's no wonder his animated form evolved so drastically. Garfield made his TV debut in the CBS special The Fantastic Funnies, seen here. Recently, the lazy feline has starred as a CGI creation in The Garfield Show, a French-American production.

The Simpsons

Image: 20th Century Fox

Thirty years ago, Fox revolutionized primetime animation, when The Tracy Ullman Show introduced a yellow family named the Simpsons in a series of shorts. This image comes from the sixth short, "Burping Contest," from June 1987. Two years later, Homer and family had their own series, which just wrapped its 28th season, seen here.