Locate a trusted community archive or modding forum (such as the Angry Birds Modding Community or GameBanana) to download the "Angry Birds Rio 2011 Sprite Pack."
If you are a modder, archivist, or just curious, accessing the actual sprites requires digging into the game’s data. Here is how to catch the changed sprites: angry birds rio sprites changed download
Never download files from sites that force you to click through multiple pop-up advertisements or install "download managers." Locate a trusted community archive or modding forum