No wai, Magnet Bomber's are way smaller. His is on the top, and they're different than all Shitennou.
But anyway, that's just me messing with him, lol! I don't really think he looks like a frog, but I DO think on this specific pixel art he is kinda weird, y'know? Specially when zoomed by the emulator: he can get real creepy.
And, hm... I dunno. All dictionaries state that it is only for clothing, but it can be the Japanese onomatopoeia for the sound that the turtle makes, much like "woof" is "wan" over there (and the dog bomber in SBM5 is called "Bonbaawan" rather than "Bomber Woof", this last one sounding somewhat stupid imo). Aaaand... Indeed it is, although Magnet Bomber seems like he is going to jump over Plasma Bomber to play wrestle or something, lol! Or maybe to kill'im, who knows?