Lost Kitties.
I've been collecting them since shortly after they came out, but they're "blind box" toys so I've got a ton of dupes and only 2 complete collections/editions (out of 11).
If my count is correct:
Series 1 has 2 collections, the main set and the XL carton set
Series 2 has 5 collections (main set, Easter sparkle edition set, Itty Bitty set, Kit-Twins set, and XL carton set
Series 3 has 4 collections, 2 of which were split into 2 "waves" for release, half coming out in late 2019/early 2020 and the other half...never being released (main set, mini cheese wheel set, cheese can set, and XL carton set.
...and I'm 90% sure that they were discontinued halfway through the last series when covid hit because I haven't seen any of the second release/batch toys from that series online anywhere and they haven't been in stores anywhere since this time last year so I'll probably have to buy on Ebay to fill in my partial collections.
Tldr; Really cute little cat toys that were discontinued part-way through the last series that I desperately want to collect all of. XD