A year ago, I got three souvenirs on a single cache – New South Wales, International Geocaching Day 2014, and one of the 7 Souvenirs of August.
This year I thought I'd challenge myself to do better yet, and I got four souvenirs on a single cache. By getting a 5/5 mystery cache I was able to get 3 of the Road Trip 2015 souvenirs (Put on Your Thinking Cap, Let's Get Extreme, and Road Trip Hero), plus International Geocaching Day 2015. I realized that if I had planned it even better by not finding any 10+ favourites caches until this one, I could have had Fun with Favorites in there as well. And if this had been a cache in another geographic location that I hadn't been to yet, that could have been a sixth souvenir on a single cache.
Has anyone done that? Or gotten more somehow?