Bite the Hand That Feeds You

To act badly toward someone who has helped you

Cost an Arm and a Leg

Something that is very expensive

Steal Someone's Heart

To cause someone to fall in love with you

Steal the Show

To attract the most attention and praise at an event

Fit as a Fiddle

To be in very good physical condition

Storm in a Teacup

A lot of commotion or fuss about a trivial matter