Do you mind playing non-thematic cards when playing the Saga Expansions?

Currently, I'm playing through the Saga expansions and while I'm trying to keep my heroes thematic, occasionally I end up with cards that aren't super accurate to the context of the quest (Ents showing up during The Ring Goes South).

I justify it by saying that while these allies may not have been part of the story, it's not unreasonable to imagine that they could have stumbled into the heroes and decided to help them. I'm just curious how everyone else plays these quest without having cards that only feature people shown in the books.