In both games power-ups are activated by getting a norn to push them.
Many felt that the introduction of power-ups in the series increased the 'adventure' aspect of the games, by forcing players to run around the map and collect objects, while reducing the artificial life aspect. Others simply found it annoying to have to collect things all over again when starting a new world (in C3). For this reason there are a few COBs/agents which activate things for you. (Need names/links.)