If a wild pokemon has a level higher than the first pokemon in your party, it can break your repels/super repels/max repels.
Bulbapedia said:The EV system was introduced in Generation I, where it was also called stat experience or Stat Exp.
The Pokémon data structure contains two EV bytes for each the five stats (HP, Attack, Defense, Speed and Special), starting at zero when caught and with a maximum EV of 65535 for each stat, however, maximum stats will be reached with only 64512 EVs. When a Pokémon is defeated, its base stats are converted to effort points and then added to the EVs. For example, defeating a Mew grants 100 effort points to each EV. (Defeating 646 Mew, therefore, will give a Pokémon maximum EVs in each stat.)
EVs are factored into the Pokémon's stats when it levels up. Additionally, EVs are calculated into stats when a Pokémon is taken from Bill's PC; this is called the box trick. A Pokémon which reaches level 100 can continue to accrue EVs up to the maximum of 65535 in each stat, and use the box trick to have those EVs factored in.
Vitamins add 2560 to one stat's EV, but cannot raise a stat above 25600. Unlike later games, the Exp. Share did not share EVs.
Bulbapedia said:In Generation I, there were only four IVs stored for each individual Pokémon: Attack, Defense, Speed, and Special. Each of these covered the respective stat, with the HP IV determined from the IVs stored for the other four. IVs had a range from 0-15, in binary 0000-1111, with the HP IV taking the final binary digit of the Attack, Defense, Speed, and Special IVs and placing it, in that order, for its own IV. As such, a Pokémon with an odd-number Attack IV had 8 added to its HP IV, Defense had 4 added, Speed had 2 added, and Special had 1 added.