Marvel Minimates are sold in the U.S. as 2-packs
to the specialty market (comic shops, Suncoast video, et al) and 5-packs
at TRU. The specialty market gets the chase figures packed one per case of 12. TRU got the 5-packs, with one figure concealed as the "hidden hero."
Single packs were developed for Target, but they passed on the first assortments. Since then, they're rumored to be back on the bandwagon. No telling how soon, though.
2-packs were also developed for Wal-Mart, but Wal-Mart U.S. also passed, while Wal-Mart Canada picked them up. These are different from the specialty market 2-packs in character teams. (They're more mass market friendly.)
Kay-Bee also showed interest in their own sets - a 3-pack IIRC - but that was dropped, too.
Currently the packaging is changing to this
for the 2-packs. It's no longer a blister, but it does make the figures look much more dynamic. I like it. (Except maybe for that "Spider-Man with Peter Head" text. Will they offer a "Robin with Dick Head" someday?)