What may have caused these blips in the value of Euro vs. US dollar
I’d go with (2j, something with how they calculate exchange rates. If you note the scale, the blips are abeolutely small, so there was just some small glitches.

I am only somewhat familiar with currencies, but the spot markets use market makers. (Currency futures are traded on exchanges, but the chart should be labelled as futures if that were the case.) Series like this are based on some kind of “average” of quotes. The period shown is outside “normal” trading hours (currency markets are global, so trading hours reflect that), and there is no reason to update quotes, so the level is mainly stable.

Any number of things could cause the small glitches. For example, if one of the dealers shuts down their system temporarily, it could move the average. Or there could have been some out-of-hours activity that caused one dealer to move quotes, and then snap back into line with the other dealers after the activity passed.