Adam sums up what every long time fan thought when they first watched Dino Thunder:
Kira: Dr. O would've loved to see that.
Adam: I still can't believe he's a doctor.
At the end of the second part, after the battle is won and the Rangers are hanging at the mansion, the writers managed to put in one last nod to SPD. Spencer walks in with a stack of toast for Bridge, and this exchange happens:
Bridge: Is it... *makes his little hand motion*
Spencer: ...The butter-est sir. *also does the little motion*
In one episode, Flurious says he has half a mind to turn Norg into a throw rug, and later says he has half a mind to shave him until he resembles a naked ice rat.
Norg: Half a mind... for a throw rug... half a mind, naked ice rat—Well, that only leaves one half left! Flurious: FIIIIIIIND MYYYYYY JEWWWWWWWWWWWELS!
In "Follow the Ranger", we get a brief glimpse into the past of Moltor and Flurious. Apparently they first started hating each other when Flurious broke Moltor's red sled as a kid.
And when they start fighting each other at the very end, Norg is standing watching on the side just muttering, "Here We Go Again", and cringing at the off screen violence.
In "Both Sides Now": "...Man law."
For context: Will has defected to join Miratrix, and Dax is venting about how you don't just hook up with your friend's ex. When Rose and Ronny turn around, he and Mack have their shoulders on each other and they say the above line at the same time.