Danifae, didn't want to search through your 505 unique pets to find the one that is still Common quality, but I challenge you to get a higher quality of whatever this mystery pet is and level it to 25.
You probably know about "buying a stone" for tradable pets. If it is a non-tradable head out and get to searching, farming, camping for a replacement. One last common to replace, you can do it.
Edit: had to go find out what pet it was. Jungle Darter from Jade Forest, that shouldn't be too hard to find better of nor to level up.