Use 'drop into' to describe a casual or unplanned visit.

Informal Visit

'Drop into' suggests the visit will be short.

Brief Stay

'Drop into' can imply a change happened gradually and hardly noticed.

The phrase often refers to unintentional shifts in behavior or state.

Indicates something or someone appears without warning.

Used to express how sudden events can have a big effect on life.

Often used when separate elements come together satisfactorily.

Can describe the moment when understanding or a solution suddenly occurs.