Examples of catchy phrases for party invitations include: "Cheers," "Let them eat cake!" and "Let the Bubbly Flow!" More specific examples might include "Hot diggity dog" for a BBQ party or, for a bowling party, "Let's get things rolling - with an afternoon of bowling!"
A popular catchy phrase that can be adapted for many "milestone" birthday invitations (that is, 30, 40, 50 and so forth) is: "Oh no - say it isn't so... The big 3-0!"
Such phrases can be used as a punchy opening to invitations, then followed by more details on the event, date, location and contact details for sending RSVPs or "regrets."