I thought I remembered an episode where willis got caught with maruijuana, am I wrong?

no sir you are correct although at this moment i cannot remember the episode title or number

However I would not expect it to be shown anymore as DS is on N@N now which is what they call a "family-friendly" network

what channel is family friendly

Nick at nite aka nickelodeon

The episode that you guys are thinking about is called "First Day Blues". It's about Willis' first day of high school. He feels
out of place and is desperate to make friends. So he meets some older guys who tell
him that they'll be friends with him if he buys some weed to take to their party. So he buys some and tries a little when the family is away. He ends up so wasted that he watches t.v without it being on. Mr. Drummond, Tootie, and Kimberly smell it when they come back and he is in major trouble.