Idle temptations.

My neighbor across the hall has entrusted me with her two goldfish for the next week. These aren't particularly high-maintenance pets, and require little in terms of direct involvement - helped by the fact that this is only for a week. There's a big one, and a little one, and maybe when the little one is too big to be eaten by the bigger one they'll be homed together. At the moment, they're in separate tanks, swimming gently on my kitchen table.

And I very much want to go to this exotic pet store and see about buying them some very nice tanks, because that's what I'd do if I got long-term ownership of goldfish.