Michael Jackson I Didn't Want to Be Moonwalkin' at 50!

7/18/2013 3:24 PM PDT BY TMZ STAFF
breaking news
Katherine Jackson
may have suffered a legal blow over some jokes her son Michael told years before his death -- specifically, that he didn't want to be a crotchety old moonwalker.

We've just gotten our hands on a portion of a transcript from Katherine's deposition in her wrongful death case against AEG Live.  Katherine says she was surprised when Michael agreed to do the "This Is It" tour because "he was always making a joke about he don't want to be doing the moonwalk on stage when he's 50 years."

Katherine's video deposition was just played for the jury.

Joke or no joke ... you can bet AEG is going to use this to convince the jury that Michael's shelf life as a performer was limited.  Translation, he wouldn't be making a lot of money by doing concerts.