CLASS vs. OBJECT and memory management

[Ñuño Martínez]

IMO, with what you're trying to achieve, it would actually be simpler to just use records and have a "spriteType" field there. You can use the Case() statement to test for the type and call the appropriate procedure when needed. It may not look the prettiest, but it's the simplest way and there's no risk that compiler optimisations mess something up.
Also, you can have a SPRITETYPE_NONE value for your spriteType, which gives you a way to have "NULL" array members for free.

This is much like how Build works, and I think I'll go this way.

Also, have you tried using a profiler? It may turn out that the memory accesses aren't really that much of a problem and you're trying to optimize the wrong thing.

No, I didn't. I tried to use GNU's profiler a long time ago (+5 years) and it didn't work too much as it couldn't identify several Object Pascal stuff. It was useless. I should try again, may be FPC 3.0 works. [edit] I've just read at the Lazarus wiki that "Support for using gprof under Linux is broken in FPC 2.2.0-2.4.0; it is fixed in FPC 2.6+", which explains why it didn't work.

Perhaps it would be more understandable if I create a mind graph representation of the concept

That would be great because I'm a bit lost.