The modern figures don't represent any one game or period, other than that the characters' styles are all "Post Sonic Adventure", so any game the came out after that, is eligable for one of these 20th Anniversary figures. Here is the MIB shot for Tails & a Sandworm enemy.

Sand Worm (came with Tails)- The design for this guy is slightly clever, he's sculpted along with the 'hole' he pops out of for attack, complete with lid. This makes it look as if it is popping up out of wherever you set it. The lid doesn't move, and is attached to the back of the worm--this is because it is solid and heavy, keeping the whole thing from tipping over. It doesn't articulate in any way. (Thought it EASILY could have, a single rotating point could have been added at the 3rd 'ball' to let you pose it without it becoming needlessly complex.)