Here are my ideas for Reaction fics, see if there's something you like. By the way, all titles are optional.
Power Rangers Watch Kyoryu Sentai Zyuranger:
When a strange energy is detected, Zordon has the Power Rangers investigate at the center of it, an old movie theater. The Rangers are trapped inside, but given a message asking if they want to see a world similar to theirs, with similar threats, but slightly different. (This can also apply to any season to watch their Sentai counterparts if you prefer a different season).
Watching the Good Old Days:
Doctors 9-12 and their assorted companions find themselves taken out of their timelines and inside of a large room with a monitor. Someone wants them to watch the Doctor way back when, back at the beginning. It's New Who watching Classic Who
Watching the Days to Come:
Doctors 1-8 and their assorted companions find themselves taken out of their timelines and inside of a large room with a monitor. Someone thinks the Doctor should have a peek into their future, to a day after they made a terrible decision. It's Classic Who watching New Who
(Those two come from my frustration that whenever someone does a 'Watching Doctor Who' story, it's always focused on the Revival. This is my idea to switch things up a bit, with both generations of the show giving their reactions to the other)
YGO Protags & Friends watch YGO Abridged:
Through some magic means, the characters of all Yu-Gi-Oh series find themselves watching a series that basically makes fun of the entire concept of the game they love.
This didn't happen in Aincrad!:
Kirito and his friends are sent a message that tells them there's a show about their time in Sword Art Online. Though reluctant to relive those days, they decide to watch...and notice something very wrong quickly. It's SAO watching SAO Abridged by Something Witty.
Z-Fighters watch DBZ Abridged:
Do I really need to explain this one?
RWBY's Rider Reactions:
You know how the story goes, the girls find a box in their room, with a letter saying it's from a doomed world, and the girls decide to watch. But unknown to them, there's a dark turn to this story. RWBY watches Heisei-era Kamen Rider, but with a twist. If you want to find out, PM me.
Total Drama Commentaries:
A DVD and or Blu-Ray compiling all Total Drama seasons is coming out, and by contractual obligation, the teens are forced to relive their experiences in the commentaries.
That's all for this one (for now), next up is Tokusatsu based stories.