Why are the House sigils not "correct" in the title sequence for season 1?

Question

Whilst researching for my answer to this related question: Where are the cast and crew logos in Game of Thrones opening credits from? I came across something peculiar. In the Season 1 title sequence some of the characters have the wrong house sigils next to their names.

For example, Emilia Clarke and Iain Glen both have Lannister Lions and Sophie Turner has the Targaryen Dragon (though there are others too):

I've seen claims this is because the actors chose their own sigils but have yet to find a reliable source for this. Though this article claims these aren't the sigils they'd pick themselves so that seems to contradict that theory.

In the later seasons these sigils have been corrected.

Does anyone know why this was the case?

Answer 1

As far as we know, an official answer doesn't exist. However, according to several fan sites/forums, see eg this Reddit discussion, it is possible that initially the actors were allowed to pick their own sigil, but this was later changed:

At the beginning of the show, they let actors choose their sigil to appear in the opening credits. Later, the producers decided to associate each actor with the family sigil of their character, to subtly guide the viewers into who's who.

Another theory is that either this was a mistake by the producers (they can happen even in productions such as Game of Thrones) or that Sansa is a secret Targaryen:

This could be a simple mistake, but Game of Thrones is a highly produced show, and it would be truly shocking if they were so careless. Then again, the only other reasonable option is that she's a secret Targaryen, and we already have one of those in the Stark family.

Unfortunately, the latter is not supported by evidence at the moment.

Since all of the above is just speculation, then I think the conclusion at the moment is that we do not know why the sigils are wrong.