All special cards can be played on any card.
When you play DOWN UNDER sometimes a situation comes up regarding playing multiple special cards at a time. The rule is that like the numbered cards, you are allowed to play multiple special cards in one play if you so choose.
For example, you might be down to the last two cards of the original 6 in your hand and they both happen to be FRESH START cards. You are wanting to get rid of them so you can pick up your face up cards. Instead of waiting two turns to play them, you can play them at the same time.
There has been a question about what happens when someone plays two REVERSE cards at once. My preference would be that if two REVERSE cards are played, then play would continue in the direction it was previously going. The next player would be the same as before. If three REVERSE cards are played then play would reverse just as it would if one REVERSE were played.
Another option would be that no matter how many REVERSE cards are played then the play would reverse as if one card was played.
I think either way is acceptable and when a group plays they can decide which way they would like it to work.