Articles before common noun followed by proper name

I would like to know if usage of indefinite articles in the following sentence is appropriate or if there should be definite articles in their place.

1) A leopard cub Leo and a tiger cub called Tig experience various
fascinating adventures and learn how to help each other and be kind.

I believe it appropriate since there is definitely many cubs in the world and we mention them for the first time, but maybe I'm mistaken and presence of proper name changes the situation? Couple of other examples:

2) An animated series about the adventures of two unfailing friends, a brown bear Innokenty and a polar bear named White Cloud.

3) Dr. Ryan Stone goes on her first space mission under the command of an experienced astronaut Matt Kowalski.

4) A popular country musician whose career is rapidly going downhill falls in love with an unknown, but very talented singer Ally.

And the opposite case:

5) Psychoanalyst Ben Sobol gets a really hard case, the New York mafia godfather suffering from depression.

I believe that since mafia godfather is a singular position, the indefinite article would be appropriate. Is it correct?

Answer

In general, if you construct the sentence to include the name of someone or something and precede the name with named, then using the indefinite article is appropriate. But if you use a proper name and do not precede it with named, then the definite article is signalled.

I want to a party with a famous singer named Madonna.

but

I went to a party with the famous singer Madonna.

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Let's look at one of your sentences:

Dr. Ryan Stone goes on her first space mission under the command of an experienced astronaut Matt Kowalski.

The construction of this sentence is off. There are several ways it could be rephrased:

(1) Dr. Ryan Stone goes on her first space mission under the command of an experienced astronaut, Matt Kowalski.

Here, I am using a comma before the name. This is a special case that I didn't mention earlier. The comma makes the mention of the name nonessential. If the name were removed, the sentence would still be grammatical.

Unless there is a previous sentence that specifically discusses an experienced astronaut, it's the indefinite article that should be used.

But, forgetting about the use case of the comma, the pattern of this sentence matches that of the one I used earlier.

(2) Dr. Ryan Stone goes on her first space mission under the command of an experienced astronaut named Matt Kowalski.

or

(3) Dr. Ryan Stone goes on her first space mission under the command of the experienced astronaut Matt Kowalski.

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This should make it clear that if we only edit the articles used, your second example sentence should be:

An animated series about the adventures of two unfailing friends, the brown bear Innokenty and a polar bear named White Cloud.

Mixing the two phrase constructions is a bit unusual, however. Unless it's an animated series only about Innokenty and a single story talks about Innokenty meeting a polar bear (which the sentence makes clear is not the case), the phrases would normally take a consistent form:

An animated series about the adventures of two unfailing friends, a brown bear named Innokenty and a polar bear named White Cloud.

or

An animated series about the adventures of two unfailing friends, the brown bear Innokenty and the polar bear White Cloud.