...Pebbles Flintstone would be almost fifty, now, with two kids (Chip and Roxy) who are almost ready to graduate high school. Fred would presumably be dead, life expectancies not being much in prehistoric times.
...Judy Jetson would be sixty-four (and presumably wondering if her boyfriend will need her, or for that matter even feed her.) This being the future, though, she might retain her youthful looks well into her second century, so that might not be so much of a problem.
...Jonny Quest is a bitter fifty-seven year old, who probably has endless therapy sessions where he talks about his intimacy issues due to his dad's inability to love him. "He thought that just giving me an Indian boy would solve everything. Well, it didn't, Dad!"
...Scooby-Doo is forty-eight (that's 336 in dog years. Actually, I think that's just "dead" in dog years.)
...Hank, the oldest member of the "Dungeons and Dragons" party, would be forty-two and probably well into the Epic Character supplements; while the youngest, Bobby, would be thirty-five and have several NPC henchmen by now.
...the Planeteers are all in their early thirties, and have emigrated to the United States due to political instability in their respective homelands. (Kwame's sick of all the "email spam" jokes. Please stop telling them.) They don't do much forming of Captain Planet these days, but they do make sure to recycle, and Ma-Ti attended a rally at the state capitol a few months ago about "going green".
...and Dexter is now twenty-three. Although he has not yet succeeded in conquering the world, it seems like more than coincidence that he got a job at Google just before they changed their stance on Net Neutrality.