Patrick "Eel" O'Brian AKA Plastic Man first appeared in 1941's Police Comics #1 published by Quality Comics, which was later acquired by DC. Eel started his career as a criminal but eventually saw the light and began fighting for the good guys after being exposed to an acid that gave him super malleability.
Plastic Man made his big debut on the 1973 Super Friends series as an all too brief guest star on the Professor Goodfellow’s G.E.E.C. episode where he was called in simply to pull a mouse out of a computer. Of all the guest heroes that appeared during that inaugural season, Plastic Man was the most shafted, even if he was the first.
In 1979, Plastic Man would return in a big way. No longer a cameo guest, he landed not only his own series, but he was the headline name on his own cartoon block of shows.
The Plastic Man Comedy/Adventure Show even introduced a live action Plastic Man between segments.
The 1979 version of the show featured tales of the bachelor hero.
In 1980, Plastic Man settled down with co-star Penny for Plastic Family and Baby Plas episodes.
In 2006, Plastic Man nearly got another animated series - which kept Plas in his hideous red jumpsuit, but at least gave him pants.
A 10 minute Pilot episode, Plastic Man in Puddle Trouble was produced, but never aired.
Instead of headlining his own series, Plastic Man was back to cameos, appearing briefly in the Justice League: The New Frontier movie.
After nearly 30 years, Plastic Man finally returned to TV in a big way as one of the primary team ups for Batman in the 2008 series, Batman: The Brave and the Bold. Along with telling Plastic Man's origin story and introducing supporting characters Woozy Winks and Baby Plas.
Later in the series, Plastic Man would be reunited with fellow Quality Comics teammates, The Freedom Fighters led by Uncle Sam.
Although not an original member of the Justice League in Young Justice, Plastic Man would be inducted during the Leagues first season expansion.
Plastic Man would also earn partial redemption for his failed pilot years earlier as 2012 would give him another chance to stretch his comedy routine via several shorts on DC Nation.
But Plastic Man is not the only stretchy guy in town. Of course Marvel also has their main stretchy guy in Mr. Fantastic of the Fantastic Four and The Incredibles has Elasticgirl (while DC's Doom Patrol has Elastic-Girl), DC also has another fairly prominent stretcher with Elongated Man. In fact Plas, and Elongated Man were seen side-by-side in Batman: The Brave and the Bold.
Elongated Man made his onscreen debut on the Justice League Unlimited series in which Plastic Man was actually referenced but never shown.
The evil Crime Syndicate version of EM appeared in the Justice League: Crisis on Two Earths movie as Extruded Man.
On the topic of evil counterparts, Batman: The Brave and the Bold's Injustice Syndicate has an evil version of Plas named Rubber Man (which actually makes more sense as a name for a stretcher).
And while Plastic Man opened the out of continuity musical spoof, Elongated Man was also part of the MAD number, That's What Super Friends are for.