Slowking is working on a thread to collect all the subtle Sentai nods in Gokaiger. If you're a Sentai buff, please feel free to contribute
Eventually we'd like to turn this into a wiki page. Speaking of which, this thread isn't for overt references. Like we already have a list of Sentai guest stars in this article (Feel free to add or correct anything if we left it out):
http://www.wolfinspace.com/wiki/List_of_previous_Sentai_members_on_Gokaiger