Currently for sale on eBay.
I found a discussion on the 1966 repeating bats wrapper being used for "B" 3rd series cards AND Bat Laffs 4th series cards over at the Vintage NonSport Cards website (Highly recommended!).
This practice was definitely "a thing".
(Click the wrapper for the link)
Here's another one (currently on eBay - different wording on the flip).
I did some searching tonight and found another listing for Bat Laffs cards in a series B wrapper auctioned in 2016 by Heritage.
I'll update the checklist (version 12.05) with this information!
(click picture for link)
Well, this is interesting! Look at these four auctions...
5cent repeater with color movie cards
Penny fold with black bat (orange back)
Penny fold with red bat "A" (puzzle back)
...the only one in the "correct" wrapper are the black bats. Now, the seller says they were found like this, so there is no guarantee these cards go with these wrappers, especially since one of the movie packs has a dupe card, but based on these and the above by Mike, we may have to relook at the wrappers Topps used for the Batman series. It may be they used whatever was available or left over, to use them up.
Here's one that sold on eBay in October 2021.
Aren't Bat Laffs cards found in the 4th series Blue wrapper packs?
Here's another GAI error. This is presented as the 1961 pack but actually is the 1966 issue. The 1961 pack has the boy with orange colored hair.
Everything we know says it should be 3rd series. Wonder why they thought it was 1st series?