What happens when you paste an app into TextEdit?
When pasting an application into TextEdit as an RTF document and saved as Rich Text Document with Attachments it creates a Rich Text document bundle, e.g. Untitled.rtfd and will contain a copy of the application pasted into the document.
The more apps you paste into the document the larger it will be.
You can check the contents of the e.g. Untitled.rtfd document bundle by selecting it in Finder and right-click then select Show Package Contents.
There you will see a copy of each application bundle you've pasted into the Rich Text Document that was saved as Rich Text Document with Attachments.