Robin Williams' Last Movie -- Ironic Scene About Alcohol

There was a crisis conference call Tuesday after Robin Williams' suicide ... with producers of his last movie trying to decide if they should delete certain scenes involving Robin's alcoholic character.

The movie is a family-friendly comedy, but during one scene Robin and his son -- played by Joel McHale -- reveal Robin's character is an alcoholic who's been sober for 6 years. Turns out Robin went to rehab 6 years before his death and was sober ever since.

Producers decided to keep the scene as is.

Production sources tell us during the 4 weeks Robin was on set in April, 2013, he was stone-cold sober and showed no signs of depression. Quite the opposite ... he was upbeat the entire shoot.

We're told there will be one change -- Robin's picture will appear as the final frame of the flick ... in memory.