I'm kicking some ideas around in my head and one of my ideas will require getting data from an input and saving it for later use by the MCU. It won't be a ton of data, just some short patterns. Any ideas about how I could do this? What kind of hardware would I need?

I think you should use the EEPROM.

#include <avr/eeprom.h>
uint8_t pattern[25] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25};
uint8_t i;
for(i = 0; i < 25; i++){
    eeprom_write_byte(i, pattern[i]);
}
for(i = 0; i < 25; i++){
    cpattern[i] = eeprom_read_byte(i);
}