This one time/ This one time when— Are both the sentences used in the post grammatically correct?

Question

This one time, I was walking down the street and I bumped into X. He proceeded to initiate a conversation, and in 20 minutes, we had had a good conversation.

This one time when I was walking down the street, I bumped into X. He proceeded to initiate a conversation.....

Is this one time usually followed by when? Or is there nothing wrong with the first sentence? Do both the sentences mean the same?

Answer 1

Both expressions

this one time
this one time when

have the same meaning. The first is an abbreviated version of the second, which is usually used when spoken.

Usually "when" is used

There was a time when
This one time when
It was during the holiday season when