Maybe you have played this game in real life where you have to take it in turns to go through the alphabet, choosing a certain theme, like, for example, 'Animals' and the first person might say 'anteater' and the next person 'budgerigar', and so on... It's quite a fun game to play on journeys and the like, but maybe that's just me.
This is ongoing in that once we've got to Z we can either go through the same theme choosing all different answers or the Z person gets to pick a new theme. I can see that certain themes could get people stuck if they don't know many cars or whatever, so try not to choose too obscure things! If nobody can think of anything for certain letters then if a little bit of time has elapsed from the last answer then we can move on to the next letter. Don't let my fresh new topic go stale!
Might as well start with Animals!
Aardvark.