I think my most embarrassing obvious lie ever was this:
Some years ago I had this two week period where I had some pretty hardcore magical thinking going on, and it manifested in particular with an acute but severe gambling issue (went away when the magical thinking went away, but I also blew over $600 in two weeks).
Anyway as part of it, I bought a ■■■■ ton of scratch off lottery tickets. Well naturally about 1 in every 4 tickets had a very small winning amount. I took all of the winning tickets in to a gas station to redeem the prize money.
Suddenly in a moment of clarity, it occurred to me that it looked really obvious that I had bought an obscene amount of lottery tickets, I think because the woman running the cashier gave me one of those concerned/judgy looks.
And in that moment the best my brain could come up with was, “I bought a bunch of these tickets for a baby shower, and then it turned out I got all the winning ones at the party.”
And then I instantly knew how obvious that lie was and was even more embarrassed. Never went back to that gas station again lol.