DS9 "Time's Orphan":
WORF: No. I am a Klingon warrior and a Starfleet officer. I have piloted starships through Dominion minefields. I have stood in battle against Kelvans twice my size. I courted and won the heart of the magnificent Jadzia Dax. If I can do these things, I can make this child go to sleep.
The only occurrence of the Kelvans that I know of was in TOS "By Any Other Name." We learn in that episode that they have tentacles, are non-humanoid, take on humanoid form, etc. Worf says that they were twice his size, so I'm guessing that he fought them in their non-humanoid form.
Do we know when this fight occurred or any details about it other then what is in the episode "Time's Orphan?"
If there's any directors notes, writers notes, companion notes, manuals, etc. that make mention of it, that'd be helpful.