While you can get married in The Sims 2 on GameCube, there isn't a specific "propose" interaction. Here's how it works:
1. Reach a high relationship level: Your Sims need to be best friends and have a high level of romance before they can even think about getting married.
2. Find the "Get Married" option: Once your Sims are close enough, the "Get Married" option will appear in the interaction menu. It's usually under the "Romance" category.
3. Choose a location: You can get married in a variety of places, including your Sim's house, a community lot, or even outside.
4. Get ready for the wedding: Your Sims will get dressed up in their finest attire and will be ready for the ceremony.
5. Exchange vows: The wedding ceremony is very simple and involves your Sims saying "I Do."
6. Celebrate: After the ceremony, you can throw a party to celebrate your Sim's new marriage.
While you can't get down on one knee and pop the question in The Sims 2 on GameCube, you can still have a fun and memorable wedding for your Sims!