A couple have been forced to warn visitors to their home to avoid sitting down - because their 12 stone St Bernard thinks it's a lapdog.
Katie and Nick Bridge, both 29, say their two-year-old pet Hercules is blissfully unaware of his enormous size.
But their huge hound loves nothing more than plonking himself on someone's knee - meaning they can't move until he decides to.
Katie and Nick say they regularly find that their legs fall asleep as Hercules stays sat on them for so long.
And they've also had to warn house guests about their pet's behaviour, in case they set in one of his favourite spots.
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Katie, from Bristol, said: "Hercules definitely thinks he is a lapdog but it's like having a fully grown man plonked on your lap.
"You really have to brace yourself because he is heavy, he weighs more than me.
"And once he's on you, you can't move until he decides he's ready to move.
"You are there for the duration, there is no way you're shifting such a big dog off your lap.
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"He'll sit on us until our legs have completely gone to sleep but he's so happy that we just can't bring ourselves to push him off.
"We have to warn anyone who comes to the house never to sit on the floor because that's Hercules' favourite place to come up and snuggle you and sit on your lap.
"If you don't want a 73kg sat on your lap, do not sit on the floor.
"When we first got him we said he would never be allowed on the sofa and we'd be really strict on it but by the time he was four months we were calling him up for cuddles.
"He loves coming up for a snuggle, especially in the evening once we've put our little one to bed. He comes up for a cuddle and takes up nearly the whole sofa."
Care worker Katie and engineer Nick, who have a four-month-old daughter Zoe, brought Hercules home when he was just eight weeks old and already 1st 10lbs.
While they felt ready for life with a big dog, nothing could have fully prepared Katie and Nick for how quickly Hercules grew with the pup piling on almost 5lbs a week.
Now fully grown, Hercules stands at 5ft 9ins when on his hind legs and ploughs through 15kg bags of dog food every two weeks.
Katie and Nick admit sharing their home and lives with their jumbo pup has come with some adjustments - the priciest of which was buying a new car.
After realising their Mazda2 would never be big enough for Hercules as an adult, Katie and Nick splashed out on the bigger £24,000 Mazda6 to cater for their pooch.
The couple also have to deal with a lot of St Bernard slobber that thanks to Hercules' height gets smothered up their walls - and sometimes over strangers' children.
But Katie says the biggest change has been allowing hours for trips that should take minutes as everyone they pass wants to meet the mighty Hercules.
Katie said: "Thankfully Hercules is as big as he's going to get now. I don't think our car would take much more.
"When he gets in you can hear that the suspension is struggling.
"We already had to buy one new car with him in mind. There was absolutely no way he would have fit into our old small Mazda2.
"It has been an adjustment sharing our space with such a big dog.
"As he's grown, we've had to move everything in our house higher and higher up so it's out of his reach.
"He loves to steal fridge magnets so we had to move them further and further up until they were all in the top third of our fridge.
"And he's always in the way so we've got used to constantly stepping over him or finding ways into cupboards he's sleeping in front of.
"We have slobber towels all over the house ready for when he's had a drink or he's excited. Sometimes you find it half way up the wall.
"We have to apologise to other people when we're out and about because he's slobbered over their pet or child. That's the worst.
"But the biggest adjustment by far has been how long it takes us to go anywhere when we've got Hercules with us.
"We get stopped all the time by people in the street.
"Everyone wants to meet him and ask questions about him. They all comment on how massive he is, how huge his paws are and so many kids shout: 'It's Beethoven'.
"Sometimes we have to leave him at home just so we can pop out quickly."
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But, despite the changes, the couple say they wouldn't have it any other way.
"Having Hercules around is definitely a lot of fun. We really can't imagine life without him. He's the best," Katie said.
"He is a loveable goof and a gentle giant, especially with Zoe. I can't believe how gentle and lovely he is with her.
"He's so chilled out when he's at home and just mooches around and flops down for a sleep.
"He loves snuggles and wants to be cuddled all the time.
"Then when we take him out he has a good run around. He's obsessed with mud and water and will swim at every opportunity.
"He's not that fussed on most dog toys but he loves his tug toy. He's so strong, playing with him is definitely making me and Nick stronger.
"I reckon he's really helped me post-pregnancy, making sure I get a good workout even though the gyms are closed."