I just haven't seen games featuring "the Fred" thing, I realized that it existed some days ago, and did some research (not quite a serious one)
Kf7 is also metioned in one of the first post in this quite old thread:
A few points about this opening. I played it sometimes during my junior years - just to prove myself I can win a game even with odds.
I. White is not obliged to accept the pawn. White can also play 2. e5 with decent and everlasting space advantage as black has no more f7-f6 to undermine white's center. White can transpose into gambit himself with 2. d4 or 2. Nf3 if he wants to.
II. (1. e4 f5 2. exf5) 2. ... Kf7? is bad, bad, bad move! Black hopes for 3. Qh5+?! g6 4. fxg6+ Kg7 5. gxh7 Rxh7 6. Qg5+?! Kh8 with rich play for sacrificed material, but now both 3. Nf3 and 3. Bc4+ give white decisive advantage (material, development, initiative).
III. After 2. ... Nf6(!) again, white finds himself on the important crossing: try to refute it in a radical way, or just play solid chess and enjoy being pawn up, or make some positional compromises to lure black into giving up more material. OTOH, black has no choices, he must play desperately.
III a. Muzio with reversed colors 3. g4?! e5! 4. g5?! Bc5 5. gxf6 0-0 (e.g. 6. fxg7 Bxf2+!) - IMHO this can't be recommended for white. Although whole piece up, white will suffer with weakened kingside and black controlling center.
III b. Solid 3. d4 d5 4. Bd3 - I consider this to be the main line of the whole system. White threatens just to keep pawn up, resume the development and maintain positional advantage. 4 ... c5! This is MY invention, my novelty or whatever you call it, and I am quite proud of it. I played dozens, maybe hundreds training games against computer in early 90's in this line to prove black has decent chances. E.g. 5. dxc5 e5 6. fxe6 Bxc5 7. Nf3 0-0 8. 0-0 Bxe6 White remains pawn up, but the open f-line gives black interesting chances. Or 5. c3 Nc6 6. Nf3 cxd4 7. cxd4 Ne4! 8. Bxe4?! dxe4 9. Nh4 Bxf5! 10. Nxf5 Qa5+ and 11. ... Qxf5 =/+.
III c. 3. Be2 - I know, some computers like it, but now 3. ... Kf7 is playable: 4. Nf3 g6 5. fxg6+ hxg6 6. Ne5+!? Kg7 7. Bd3 Rh6 and black captures center with pawns and with h-line gets huge compensation for a pawn, because white's attemp 8. Ng4?! Nxg4 9. Qxg4 e5! 10. Bf5? Qf6! doesn't work.