I just read a trivia fact and I’m looking for verification. It was that in the Lord of the Rings trilogy, Legolas only speaks one line directly to Frodo; in the council meeting when he says “And you have my bow.” In all other scenes where they’re both present, Legolas only either speaks to other characters or to a group of characters which includes Frodo.
I could spend twelve hours rewatching the trilogy to see if this is true. But I figured it would be easier to throw it to the crowd here.
Are you asking about the books or the movie?
One thing to keep in mind is that for all of The Two Towers and almost all of The Return of the King, Frodo and Legolas are in different places.
In the book, after leaving Lothlorien, Frodo is trying to make out the length of their stay when Legolas replies something to the effect of time being different for the elves.
Asking trivia about the movies is kind of silly. What happens over 9 hours or so compared to what happens over 1500 pages… 
Yes, Legolas is only around Frodo for a limited time. From the beginning of Book 2 (the second half of The Fellowship of the Ring) to the end of that book (when Frodo and Sam head off to Mordor by crossing Anduin). They don’t meet up again until after the Ring is destroyed, and even then they are only together for a couple chapters, while Aragorn is crowned and the Fellowship makes its way back home. Gimli and Legolas leave the party at Isengard, IIRC, so Gimli can be taken through Fangorn Forest.
I’ve also heard “trivia” that said in the making of the* Lord of the Rings* movies, that Ian McKellan and Elijah Wood never actually film any scenes together. Now I’ve seen a little bit of behind the scenes clips and I’m pretty sure I saw them filming together, just posed at different angles for the forced perspective.
What does sadden me though, is that apparently it’s been said that Ian McKellan did most if not all of his scenes in *The Hobbit *Trilogy by himself with a green screen. That had to be rough on the poor guy.
Yeah, that’s completely untrue, and you have seen clips of them together. Here’s just one scene of them together showing the force perspective tricks they used.
There is the scene (that I can’t find) where he’s by himself while talking to a bunch of tennis balls filming the dinner at Bilbo’s scene, and breaks down in tears. But there were plenty of other scenes where he’s with other actors - like here. Note that a ton of in studio filming was done on a set, but with a green screen background so they could CGI in whatever was supposed to be in the far background.
Tolkien took out the line where Legolas asks Frodo why he doesn’t just ride to Mount Doom on an Eagle.
It’s Jodie Foster and Anthony Hopkins who have hardly met, despite making Silence of the Lambs together. You can hear her talk about the fact that they have basically never spoken in this video.
Ian McKellan did initially film scenes via green screen for the Hobbit movies, but I do think they resolved a lot of these terrible issues when they left the Shire. He was miserable for quite awhile, though.
So, ignoring that the OP should have said “LoTR movie trilogy,” is it true? Is that the only line that Legolas speaks to Frodo in the movie trilogy?
Sounds about right. I don’t think Gimli talks directly to Frodo much more either.
It’s kind of an odd requirement. Legolas & Gimli are only with Frodo at the Council of Elrond and as part of the Fellowship. During the existence of the Fellowship, they’re nearly always all together. So conversations would normally be within the group, not one on one anyway. The only one on one conversations in FoTR post-Council I can think of involving Frodo are either with Sam (incessant), Boromir (lend me the ring), Gandalf (talking about the Door to Moria) and Aragorn (post-Boromir insanity).
No, silly, it was Gandalf’s idea! 
Note: While Little Nemo’s link itself is safe, the site it’s on is mostly NSFW, as are some of the ads. As such, I’ve put it in a spoiler box to comply with the two-click rule.