Ray and Zari can be heard singing at various points in "Sweet Baby James", though neither of their mouths are moving except in Zari's solo at the beginning.
Gideon mentions the anti-meta-human act of 2029, but it was previously mentioned that that law came into effect in 2021, However, it's possible that ripples due to time travel caused the law to come into effect later than it had in the previous time-line, or that two Acts of the same name, passed in different years, exist, as often occurs in the real world.
To promote Heyworld, Gary, Nate, and Sara dress up, respectively, as Green Arrow, the Flash, and Supergirl. But while she may have crossed over from her own Earth a handful of times, Kara/Supergirl doesn't exist on Earth-1, so a large portion of the customers that the Legends are trying to attract likely wouldn't get who Sara is pretending to be.