I've been wondering this for a while, can you fit the G1 Headmaster figures like Spike into the Micromaster bases like Groundshaker? Would they be too small?

 

Headmasters and Micromasters are generally the same height, but Headmasters are less bulky. It might work.

 

Not perfectly, but yeah, sort of. A lot of them have articulation in different ways (especially the powermasters) than many micromasters, but they don't look too awful.

 

Powermasters...because it was about time Transformers could do the splits.  

 

Having Hi-Q ride Powermaster Prime's grey turrets in base mode ruled and you know it. C:

 

Someone needs to take pictures of the Powermasters and Blaster doing yoga.