Christopher McDonald was slinging brew like the Germans do during Oktoberfest -- which could help explain his DUI arrest later the same day.
TMZ has obtained video of Chris at an Oktoberfest Saturday around the Lake Arrowhead area, and as you can see ... he was front and center for the festivities, beer in hand and all.
Unclear how much this plays into his bust later that night, but we do know he was arrested for DUI and thrown into jail just hours later. We're told this video was taken around 5 PM ... about 4 hours before he crashed his Porsche and was taken into custody.
As we reported ... Chris allegedly tried playing the celeb card with cops, but they weren't buying what he was selling -- which is apparent in these arrest photos. He was taken to a nearby jail and was set to be released without bail.
Fahr vorsichtig, Chris.