How far did you watch? Up to Alien Rangers?
The last of the original Rangers left in Turbo. There was a ceremony where they handed their powers off to the new team.
The next season, Adam comes back, but his morpher is damaged, and he can't stay morphed for long.
Lost Galaxy kept Bulk around, though he only made two or three appearances.
For the tenth anniversary, Jason and Tommy returned, as well as Zedd's Zord,Serpenterra.
Bulk and Skull got a cameo too.
Jason Frank came back again in Dino Thunder, in a regular role as an older Tommy,Dr.O. He was a teacher.
One episode had him fight illusion versions of his past Ranger personas.
Don't ask why there's a silver stripe on the Green Ranger's helmet, they never explain it, and fans get pissy if you bring it up.
Tommy returned the following season, but not played by Jason Frank. He was just a voice played by one of Dino Thunder's actors.
Rita kinda comes back in Mystic Force. She's dubbed absolutely horribly by a new actress.
Her appearances are so brief and jarring I wonder why they bothered.
For the 15th anniversary, Adam returned once again, to lead a team of past Rangers.
They fought Thrax, son of Rita Repulsa and Lord Zedd!
Don't ask about his age, it makes no sense.
Alpha also returned, but it's not Alpha 5, it's Alpha 6, on Earth again for sone reason that goes unexplained.
RPM had a toy commercial
that tried to tie in with Mighty Morphin, through the RPM Rangers finding the MMPR suits in the wrecked Zeo Command Center.
The season following RPM was a remastered and edited MMPR(the first 32 episodes) and it's fairly unpopular, but we did get this kinda cool music video
Samurai brought back the old theme, reworked to fit the new season. Bulk came back, and he was taking care of Skull's son!
At the end of Super Samurai(Samurai's second half) Skull returns!
Megaforce name drops Zordon, and has some little homages to MMPR, but it's not really connected in any meaningful way.
It's second half, Super Megaforce, had the new team morph into the old suits.
There's a name drop or two, and Tommy shows up for a few seconds at the end.
Super Ninja Steel was the twenty-fifth anniversary, and brought back Tommy…again. This time it's established he has a kid,JJ. He also may or may not be married to Kat.
Rocky also shows up as the Red Mighty Morphin ranger.
The episode, Dimensions in Danger is about some new villain who only shows up in that episode, but everyone acts like they know him. He's kidnapping Rangers from different dimensions, even though we only see Rangers from the "primary" dimension. He uses their power to create evil robot duplicates.
Beast Morphers had Jason return and it sucked really hard.
His power coin was in a meteor(no explanation), the bad guys revived Goldar, but he looks and sounds totally different, the other MMPR rangers are just silent suits, Jason never fights Goldar, then we get a "moral of the day" where Devon, the Beast Morphers red ranger tells Keeper, a character from Dino Charge,he should have listened to him when he told him a meteor was going to hit him. The end. Beast Morphers is not my favorite.
Currently we have Dino Fury, so far, not much connection to MMPR, but some absurdly obscure characters from an old episode are here. The Morphin Masters, who were mentioned once in one episode and then popped up in the comics.
Oh, and Zedd came back. I forgot, because so do the Rangers.
His original voice actor passed away, so he has a new voice. It's alright.
There's also the 2017 movie that's a reimagining of the origin of MMPR.