For something this rare, the BF’s very underwhelming. The other catsack items are at least somewhat unique, but this one has a number of better replacements ready to be bought.
Don’t worry, that was the plan from the beginning. The dialogue system wasn’t finished at the time and wasn’t that prioritized either. He will use the pet system as well. He is your friend.
When we finish the Cosmic Catsack, I’ll finish him up. I plan to use him as a test for the pet system as well.