Spoilers ahead for Henry Danger, if you haven’t seen it, proceed with caution.
In 5 of the last 11 Henry Danger episodes (in airing order), there was an additional scene after the credits that each set up the series finale. But these scenes don’t appear on Paramount+, and there are no DVD’s of this show AFAIK.
At the end of Mr. Nice Guy, which premiered on January 11, 2020, the Bigfoot hunter from the episode “My Dinner With Bigfoot” (I can’t remember his name) shows up and proves that cavemen are real by showing a caveman frozen in ice. He opens his eyes, and the hunter runs screaming and drops his camera. It turns out to be Drex after he was sent 100 million years into the past at the end of Back To The Danger Part 2.
At the end of Theranos Boot, which premiered on January 18, 2020, the hunter brings Miss Shapen back to the mountain where he saw the caveman, because she promised she’ll marry him if he can prove the existence of cavemen. They both run away screaming (and the hunter leaves his camera again) after hearing a noise, and Drex looks down at the camera.
At the end of Rumblr, which premiered on January 25, 2020, Drex is shown thawing out the last remaining member of his caveman army with a blow dryer. Bigfoot asks him to leave because the mountain is his, but Drex whistles for the other cavemen, who come out, and Bigfoot leaves them alone.
At the end of Cave the Date, which premiered on February 1, 2020, Drex is shown with the rest of the cavemen shaving in the women’s room, and the security guard from I Dream of Danger asks them to leave so that she can sit on the toilet and consume a whole bag of nacho cheese.
At the end of Escape Room, which premiered on February 8, 2020, someone from the club in the Rumblr episode opens a tube with a phone, and on that phone plays a video of Rick Twiddler, who says that there are blueprints for the Omega Weapon inside.
AFAIK, these scenes only appeared on their first broadcast on the main Nickelodeon channel and were never seen again. Some people have uploaded videos on YouTube of them, but they were all recorded from their phones, and not all of the scenes were preserved.