Egg level up.
You may have already noticed but when you use the R = Quick level up AR cheat the 2nd and 3rd Pokemon in your party may also grow levels.
If you put an egg 2nd or 3rd and use the cheat the Pokemon in the egg will grow levels.
You cannot teach it attacks though until it has hatched. The Pokemon goes back to Lv.5 when it has hatched.
P.S. I haven't checked but if it grows a level then hatches, I think the stats won't go back down.
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