Back to Basics (campaign) Puns

Context: I'm in a DnD campaign, for fifth edition.

So basically, one of my characters told a horrible pun to a planetar (Massive angel-like being) over Sending (A spell letting you communicate over long distances). "Whaddya call a celestial who likes to fish? An angel-er." and then he got asked to put his journal in the box that suddenly appeared behind hm, He complied, and when he got it back his name was gone from the first page of the book, and there was a golden box, that read "Tell me what I've pun, wizard" So I'm assuming he needs to answer in some sort of pun related to his name, Klaus Hallowmantle.

However, my brain is smoother than... I can't think of anything to compare it to all of a sudden. Oh well. Anyone who can help me with this?