I think magical mishaps is a great fit for the "mirth and mayhem" tag line, nothing like it to make magic that little bit more fun and unpredictable.
Nothing with a massive detriment to the caster of course, just all those funny "whoopsies" like unintended target, random spell, teleport, accidental polymorph and the like.
We always had fun with magic mishaps at our table, creates some unintended and funny problems a lot, feels like a perfect fit for what the games want to do in my opinion.
Could be optional rule as well, if its not everyone's cup of tea.
What do you guys think?