CCK 4.7 content types use the standard title field, but not the body field of the node table in the Drupal database.

In Drupal 5.x content types no longer belong to CCK. They use the title field, and allow you an option to use the body field.

So, what happens if you populate the body and teaser fields in the node table in Drupal 4.7, by inserting them into the database directly, or using a custom module like nodeimport? And what happens when you then upgrade to Drupal 5.x?

While still in Drupal 4.7, the information in the body and teaser fields of your CCK node will not show up in any presentation of your node. However, the information in the table will survive an upgrade to Drupal 5.x, because CCK will not be doing anything at all with it.

This behaviour is described in a CCK issue, and has been confirmed with a little testing. It is nevertheless largely uncharted territory, so you should definitely have a good backup before trying it, plus try it in a test environment first just to be sure.