This would be great for a large group.
Get a whole pile of big flannel shirts from a local thrift store. Get two different colors, perhaps red and blue vs. blue and green. These can be kept for future games, sewn shut and stuffed and donated as pillows to a homeless shelter, or given out to the less fortunate kids afterwards.
Play blob tag exactly as you would before EXCEPT: Have two girls and two guys start out being ‘it’. The two girls put the flannel on the two of them, with one arm out each side, and button it up. Then they have to gallop around as a two-headed, four legged person. The guys do the same thing. Then when they tag someone, they have to join up with them. Once that person tags another person (preferably of the same gender so as to avoid any problems) then that new person has to get into a flannel shirt of the same color with that person and then they gallop around trying to catch people. Also, if they tag another two headed four legged creature of another color, they are then their color and have to change their flannel! The game finally ends when one color dominates overall.