Get him a hamster. Haha...

Actually, I was going to recommend an adult beardie or a leopard gecko. Both are very mellow and pretty tolerant. A beardie would just latch onto his shirt and stay there pretty well. Both of them thrive in desert vivaria, which is pretty easy to maintain. A three year old is a bit young for herps of his own... maybe make certain the lid stays latched/locked unless mommy or daddy are in the room?

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Holly

1.0 Florida Kingsnake (Eddie Gein)
1.0 Bearded Dragon (Charley Manson)
1.0 Fire Skink (Peter Dinsdale)
1.0 Vietnamese Golden Gecko (George Chapman)
0.0.1 Blue Day Gecko (Joe Ball)
1.0 Orange Marmalade Cat (Oliver)
1.0 Black Cat (Shadowfax)
1.0 Tennessee Walking Horse (Durango)

2.0 Toddlers (Justice & Trevor)