I don't mean to imply there's any serious mischief in it.

But a further change would be necessary even then before serious mischief could result.

The serious mischief of the convention was that it made it impossible for an Athenian to write a play.

Her eyes took on the slight crinkle of serious mischief.

A magic charm had helped guide him and keep him from serious mischief.

To think this success renders unimportant a previous failure, when in fact they're two entirely different species, could lead us into serious mischief.

Just you do prevent any serious mischief.

A friend of Jack's said he saw you coming out, looking like you'd just done some serious mischief.

The grandfatherly expression said the grandchildren had been up to some very serious mischief indeed.

I think it calculated to work serious mischief.