As our resident 'Timedude', I must say that building a Tardis is a pain in the ass. The only one I ever made wasn't able to open or anything. But, back on topic....
I think A.B. is right. A Ker-Timetravel table is in order. As I recal, there was something like that in an older game. But anyway, here's a start:
1. The minifig disapears, going 2 rounds into the future!
2. The minifig disappears, reapearing 1 round latter with a few pieces of advanced tech.
3. Random other fig replaces existing fig. (should be differnt unit type)
4. Fig comes back with an evil twin from the dark-universe.
5. Minifig disapears. Next round, time machine re-appears, without anybody in it.
6. Time machine returns with 4 additonal units, unallied with either side.
8. Rip appears in the time space continuum. Half minifigs disappear, battlefield is radically chanced, new army enters the scene, ect....
I' running out of time , so you guys can finish the rest. I'll be back tommarrow....