Find out why. Talk to him, and ask him what's wrong.
Chat with our AI personalities
Embrace their uniqueness and accept them for who they are. It's important to be understanding and not judge them based on their differences. Ultimately, a true friend will appreciate and value your support in spite of any quirks.
If by weird you mean that your friend seems to be in danger of some kind, then get help right away. If by weird you mean goofy or fun loving, then join in. Life is too short.