Those pillows belonged to his favorite knight who always sat at Arthur's right.
5 seconds sound clip from Snagglepuss - Knights and Daze (S1E10).
You can hear this line at 00:00:36.687 in the Blu-ray version of the episode.
Quote context
[...]
- Cluck-cluck-cluck cluckity-cluck-cluck-cluck. Cluckity-cluck and a err-err-err-err-err even.
- This castle belonged to the brave and noble King Arthur of whom history tells us much.
- In this room is the famous round table where he met with his knights.
- And that is King Arthur's chair.
- What are those pillows doing there?
- Those pillows belonged to his favorite knight who always sat at Arthur's right.
- Why did he have to sit on pillows?
- Well, the story goes something like this.
- Once upon a time there was a knight known as Snagglepuss the Lion-hearted.
- It figures. If I were a chicken, I'd be chicken-livered.
- Snagglepuss' lifelong ambition was to become a member of King Arthur's knights of the round table.
[...]