It's one thing to surprise a lovely girl & go down deep in her nether-region with your talented tongue just because you know it makes her happy...
It's another thing ENTIRELY when she gets that naughty gleam in her eye & pulls her cheeks apart as she squats directly over you; grabbing the back of your head & shoving it hard up her rear-end, making you lick & lap at her asshole, riding your face & rubbing her sweet ass all over your lips & mouth, just because she knows it makes her happy...