Well, although these are focused on kids more than adults, there’s quite a few
My Little Pony Role Playing Games out there that are based on the usual D&D rules,
complete with expansion packs, and you can even find some D&D specific
props from the Hasbro store, like these dice, and some people have done
write-ups of their experiences with the game system, so there’s lots of sources of pre-made adventures that you can try out solo or with a group.
And I’ve had really good luck adapting the for-kids rules and scenarios to adults - sometimes with very few tweaks (especially if drinking is involved). The games are a little lighter and, frankly, can be a lot of fun. There’s a lot more running around and screaming, it’s less harsh when things go completely ass over tea kettle, and the scenarios make for some really good drinking time gaming.
Check out some of those game sets - they come with scenarios all prepared, and if you want something rougher, just turn the dial up to 11 on the encounters and mobs.
Honestly, for myself? The more I bring MLP into gaming, the better the games are. Whether I’m playing with a crowd or by myself.
Friendship - just add drinks and gaming and you’ve got magic.
