The scene of Tom's belly getting bigger after drinking water has appeared in many episodes of Tom and Jerry, but not all versions have this plot. You may need to provide more background information or description to help determine which episode is specific.

Please note that there are many versions in Tom and Jerry, including different animation companies, different times and backgrounds, different language versions, etc., so the specific scenes may vary from version to version. If you can provide more details or specific versions of information, then I can answer your question more accurately.