Substitutions are definitely possible for Creepy Crawly and Tolai Hare. Lovebird Hatchling is a must have.
For Creepy Crawly, any Critter with >260 Speed rating with Flank, Survival and Apocalypse will work. For Tolai Hare, any Critter with >260 Speed rating with Flurry, Dodge and Burrow will work. For both pets, get the one with the highest Power stat.
A possible mishap is that B/B Creepy Crawly, with only 1400 Health, might be killed by backline damage. If that happens, restart the match.
ADDENDUM: Please note, you just need the Creepy Crawly and the Tolai Hare (or their substitutes) to be faster than 260. S/S is NOT recommended because of its low power stat. Faster than 260, highest power stat you can get.