get into/in the act, to

To thrust oneself into another’s conversation, performance, undertaking, or the like. The term comes from the theater and is analogous to another theatrical cliché, STEAL SOMEONE’S THUNDER. The American comedian Jimmy Durante popularized it from the 1930s on with his frequent complaint that “Everybody wants to get into the act” (cited by Eric Partridge in his compendium of catchphrases). It no doubt originated years earlier in vaudeville.