Hmmm, I assumed Alka-Seltzer was known world wide, like Coca Cola. (I see I badly misspelled it.) Speedy was a little animated guy from the period of the jingle, "plop, plop, fizz, fizz; Oh, what a relief it is!" He flew around like Peter Pan, as I recall.
I always blamed it on the tryptophan in the Thanksgiving turkey!