I fulfilled a childhood dream when I became [the] champion

[Silverobama]

I wrote the following sentence:

I fulfilled a childhood dream when I became the champion.

This was written by me. I wanted to say that I finally realized my dream of becoming the champion of something (sorry I don't remember), I wrote the sentence in 2012.

Is the "the" needed here?

 

[Tarheel]

Yes.

It must happen quite a bit if you don't remember what you were the champion of.

 

[Rover_KE]

You need something else for context. If you don't remember, make something up – as I'm going to:

I fulfilled a childhood dream when I became the champion of the school's javelin-catching competition.

As a boy, I loved eating caterpillars. I fulfilled a childhood dream when I became champion of the town, with a record of 36 in one minute.

 

[Tarheel]

I'm not going to volunteer for either of those.

 

[jutfrank]

You can use 'champion', without 'the', if it's meant as a title, whether official or unofficial. Similar cases:

I want to be leader today.
She'll be made deputy within a year.
He was voted president for the third time.
Arsenal are going to be runners-up again this season.

In all of these cases, you're not referring to the thing itself, so you don't need a reference word (an article). Instead, you're really talking about the role or position or title that the thing itself is assigned.