Here's my another "Impossible Puzzle" my friend brought to me, after solved her puzzle the day before (with your help for sure).
Any ideas?

White to mate in three.

White has 4 queens. Black has a bishop. Not impossible.

It's clear to me that the first move involves the central Knight moving to b8, d8 or a5, all of which deliver a discovered check and force Bb7 (Ne7 blocks the advanced Rook from protecting the Bishop on a7, thus gives Black options).  After that, I'm looking at an open c-file for that Rook to join the attack, but after Rc8+ Kxa7 I can't see how to sink that dagger.

1. Be6 Bd7! 2. Qg8+ Kb7 3. Qb8+ Ka6 4. Qb6#

definitely gives mate but in four.

What about Qg7 forcing the black bishop to move off the back rank. If the bishop maintains protection of the b7 square with Ba6, white checks with the queen on g8, black intervenes with the bishop on c8, then Qxc8 is check mate in 3.

Otherwise, black's only option is to block immediate access to b7 with Bd7, tempting Qxd7 (and so obtaining a draw). But in this case white declines the bishop and checks, as before on g8. The black bishop is obliged to block on c8 again, and Qxc8 check mate in 3.

If black does anything else - then its mate in 2 with Qb7.

After 1. Qg7 comes black with 1... Bd7!. White can't take Qxd7 because of stalemate. If you do 2.Qg8+ black comes with 2...Kb7!! and there is no mate in 3

Stratajee What if 1. Qg7 Bd7! 2. Qg8+ Kb7!

Yes Adriandmen and RetiFan...you are correct. I went too fast. Trickier than I thought.

In this case....the its Rc7. Black has to move the bishop, but this time, whatever he does, Qg8+ bc8, Qxc8 results in mate in 3.

Consider me stupid, but, a puzzle like this doesn't seem to matter if it's mate in 3, 4, or 5.

Forgive me for being serious for a minute, but white wins.

1. Rc7 Be6! and stops Qg8?

No...no good. Black plays Bb4. Sorry. 

The question is not whether white wins, the challenge is to do it only in three moves, If this sounds dumb to you, why bother to comment at all?

EDIT: Corrected a typo at 'wheter'.

Bg4 I meant. mmmmm bit too impulsive. I'll shut up.

Stratajee Actually 1. Rc7 Bg4?? 2. Nd8#

The nasty problem is that White cannot afford to waste time to prepare checkmate or whatever zugzwang he has in mind since Black has always Be6!, threatening to check with Bxd5+ and no more checkmate in 3 possible. Also the direct Na6+ leaves the a7 bishop unprotected after Bb7 and White is faced again with the "threat" of Bxd5+ with check. This one really a toughie...

Not to mention Black King always have a6 for safe haven...

haz0rd

What if 1. Rb7 Kxb7

Actually, 1.Rb7 was my first attempt but then Kxb7 and black has always Ka8 or Ka6 to hide away and don't see anything concrete for White here...