The mnemonic for remembering the symbols in order
I Very eXcitedly Licked Chocolate Dessert Morsels: I(1), V(5), X(10), L(50), C(100), D(500), M(1000). Another version: I Value Xylophones Like Cows Do Moo. The ascending order is the key — memorise the seven symbols and their values and the rest follows from the additive/subtractive rules.
Reading film copyright years quickly
End credits show production years as Roman numerals. A quick method: identify the M's (thousands), then CM or D+C combinations (hundreds), then XL/XC/L+X (tens), then IV/IX/V+I (units). MMXXIV: MM=2000, XX=20, IV=4 = 2024. Practice with a few years and the pattern becomes instinctive.
Why clock faces use IIII instead of IV
Most clock and watch faces use IIII for 4 rather than the "correct" IV. Several theories exist: visual balance (IIII balances VIII on the opposite side better than IV does), tradition from clockmakers who historically used IIII, or that IV was the beginning of IVPITER (Jupiter) which was considered disrespectful in ancient Rome. Whatever the origin, IIII on a clock face is considered correct by convention even though it breaks the usual subtractive rule.
Super Bowl Roman numerals — a quick cheat
Super Bowl I was played in January 1967. Each subsequent Super Bowl adds one. Super Bowl 58 (LVIII) was in 2024. To decode any Super Bowl Roman numeral quickly: L=50, then add or subtract the remaining symbols. LVIII = 50+5+3 = 58. The NFL briefly abandoned Roman numerals for Super Bowl 50 in 2016 (because "Super Bowl L" looks awkward) before returning to Roman numerals for Super Bowl LI.