Blake Lively and Ryan Reynolds were the hot topic of conversation among guests at ‘Saturday Night Live’s 50th-anniversary show and after-party — and it all had to do with the couple’s ongoing legal battle with Justin Baldoni … TMZ has learned.

Three sources with direct knowledge tell TMZ … lots of stars who attended the ‘SNL’ events on Sunday night were “confused” as to why Blake and Ryan appeared at the show while they battle it out in court with Baldoni over drama surrounding the movie, “It Ends With Us.”

As you know, the two sides have accused each other of waging smear campaigns, and Blake has also claimed Justin sexually harassed her while on the movie set.

Another source who attended the soiree following the show was overheard saying, “Who told them to come?” … referring to Blake and Ryan.

However, another eyewitness says the famous couple was super popular at the ‘SNL’ show, with fans cheering from behind barricades when the two rolled up to 30 Rock and got out of their car.

That witness also says Blake had a “nice interaction” with Dakota Johnson, and Blake and Ryan hit it off with Woody Harrelson while they were all in line for the red carpet.

After the show wrapped, the source says Blake and Ryan stayed in the 30 Rock studio for an hour, mingling and taking selfies with other actors, cast and crew.

We’re told Blake and Ryan finally left the studio with Paul McCartney, before they skipped the after-party and went home because it was already late.

One more thing … this source says Justin Baldoni’s name never factored into any of their convos.